Chemically amplified negative resist composition and patterning process

ABSTRACT

The present invention provides the chemically amplified negative resist composition comprises an onium salt represented by the following general formula (0-1), a resin which becomes alkali insoluble by an action of an acid and an acid generator, 
     
       
         
         
             
             
         
       
         
         
           
             wherein R f  represents a fluorine atom or a trifluoromethyl group; Y represents a cyclic hydrocarbon group having 3 to 30 carbon atoms, the hydrogen atom in the cyclic hydrocarbon group may be substituted by a hetero atom itself or a monovalent hydrocarbon group which may be substituted by a hetero atom(s), and the hetero atom(s) may be interposed into the cyclic structure of the cyclic hydrocarbon group and the monovalent hydrocarbon group; and M +  represents a monovalent cation. There can be provided a chemically amplified negative resist composition which can improve resolution at the time of forming a pattern and give a pattern with less line edge roughness (LER).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a chemically amplified negative resistcomposition to be used for processing of a semiconductor or photomaskblanks, etc., and a resist patterning process using the same.

2. Description of the Related Art

In recent years, as an integrated circuit progresses toward a higherintegration, a finer circuit pattern profile has been required. Amongthese, a chemically amplified resist using an acid as a catalyst hasbeen exclusively used in the patterning process of the size of 0.2 μm orless. Also, a high-energy beam such as ultraviolet beam, far ultravioletbeam, an electron beam, etc., has been used as an light source at thistime, in particular, an electron beam lithography which has beenutilized as an ultrafine processing technology is indispensable as aprocessing method of a photomask blank when a photomask for asemiconductor manufacturing is to be produced.

A polymer containing a large amount of aromatic skeletons having anacidic side chain, for example, a polyhydroxystyrene, has been utilizedas a resist composition for KrF excimer laser, but it shows remarkableabsorption in wavelength of near 200 nm of the light, so that it hasbeen never used as a resist composition for ArF excimer laser. However,it is an important material in the point that high etching resistancecan be obtained as a resist composition for an electron beam or a resistcomposition for extreme ultraviolet (EUV), which is a useful technologyfor forming a smaller pattern than the processing limit by ArF excimerlaser.

As such a resist composition to be used for photolithography, there area positive type in which an exposed area is dissolved to form a patternand a negative type in which an exposed area is remained to form apattern, and a type which can be used easier is selected depending onthe form of the resist pattern to be required. The chemically amplifiednegative resist composition generally contains a polymer which isdissolved in an aqueous alkaline developer, an acid generator which isdecomposed by exposure light to generate an acid and a crosslinkingagent which forms crosslinking between polymers using an acid as acatalyst to insolubilize the polymer in the above-mentioned developer(in some cases, the polymer and the crosslinking agent are integrated),and a basic compound to control diffusion of the acid generated by theexposure is further added in general.

As the alkali soluble unit constituting the polymer which is dissolvedin the above-mentioned aqueous alkaline developer, a type of using aphenol unit may be mentioned. In the prior art, a large number of such atype of the negative resist compositions have been developedparticularly for exposure by KrF excimer laser beam. However, a phenolunit thereof does not have light transmittance when the exposure lighthas a wavelength of 150 to 220 nm, so that these have not been used as acomposition for the ArF excimer laser beam. But in recent years, it hasbeen attracted attention again as a negative resist composition forexposure light of a short wavelength such as an electron beam (EB) andEUV which is an exposure method for obtaining a finer pattern, and, forexample, Patent Document 1, Patent Document 2 and Patent Document 3 havebeen reported.

By the way, in the above-mentioned photolithography, for the purpose ofcontrolling resist sensitivity or pattern profile, various improvementsby selection or combination of the materials used for the resistcomposition, and modification of the processing conditions, etc., havebeen investigated. As one of the focuses on the improvement, there is aproblem of diffusion of an acid which causes important effect onresolution of the chemically amplified resist.

An acid diffusion controlling agent is a material to suppress aciddiffusion, and is in fact an essential component to improve performancesof the resist, in particular resolution. Various investigations havebeen done on the acid diffusion controlling agent, and amines or weakacid onium salts have generally been used. As an example of the weakacid onium salt, in Patent Document 4, it has been disclosed that goodresist pattern can be formed without forming T-top, difference in linewidths between isolated pattern and dense pattern, and standing wave byadding a triphenyl-sulfonium=acetate. In Patent Document 5, it has beenstated that sensitivity, resolution and exposure margin have beenimproved by the addition of a sulfonic acid ammonium salt or acarboxylic acid ammonium salt. Also, in Patent Document 6, it has beenstated that a resist composition for KrF and an electron beam comprisinga combination containing a photoacid generator which generates afluorine-containing carboxylic acid is excellent in resolution, andprocess admissibility such as exposure margin, depth of focus, etc.,have been improved. Further, in Patent Document 7, it has been alsostated that a resist composition for F₂ laser light comprising acombination containing a photoacid generator which generates afluorine-containing carboxylic acid is excellent in line edge roughness(LER), and a problem of footing profile has been overcome. Whereas theproposals of the above-mentioned four documents relate to thecompositions used for KrF, an electron beam and F₂ lithography, inPatent Document 8, a positive photosensitive composition for ArF excimerlaser exposure containing a carboxylic acid onium salt has beendisclosed. These are to suppress the acid decomposition reaction of theacid-labile group and make the acid diffusion distance small (tocontrol) by exchanging a strong acid (sulfonic acid) generated from theother photoacid generator by exposure with weak acid onium salt to forma weak acid and a strong acid=onium salt so that a strong acid (sulfonicacid) having high acidity is exchanged to a weak acid (carboxylic acid),and thus, it apparently acts as an acid diffusion controlling agent.

However, when patterning is carried out by using the above-mentionedresist composition containing a carboxylic acid onium salt or afluorocarboxylic acid onium salt, it involves the problem that LER islarge, so that development of an acid diffusion controlling agent whichcan reduce LER has been desired.

PRIOR ART DOCUMENTS Patent Documents

[Patent Document 1] Japanese Patent Laid-Open Publication No.2006-201532

[Patent Document 2] Japanese Patent Laid-Open Publication No.2006-215180

[Patent Document 3] Japanese Patent Laid-Open Publication No.2008-249762

[Patent Document 4] Japanese Patent No. 3955384

[Patent Document 5] Japanese Patent Laid-Open Publication No. H11-327143

[Patent Document 6] Japanese Patent No. 4231622

[Patent Document 7] Japanese Patent No. 4116340

[Patent Document 8] Japanese Patent No. 4226803

SUMMARY OF THE INVENTION

The present invention has been accomplished in view of theabove-mentioned circumstances, and an object thereof is to provide achemically amplified negative resist composition improved in resolutionat the time of forming a pattern, and can give a pattern reduced in lineedge roughness (LER).

To solve the above-mentioned problems, the present invention is toprovide

a chemically amplified negative resist composition comprising an oniumsalt represented by the following general formula (0-1), a resin whichbecomes alkali insoluble by an action of an acid, and an acid generator,

wherein R^(f) represents a fluorine atom or a trifluoromethyl group; Yrepresents a cyclic hydrocarbon group having 3 to 30 carbon atoms, thehydrogen atom in the cyclic hydrocarbon group may be substituted by ahetero atom itself or a monovalent hydrocarbon group which may besubstituted by a hetero atom(s), and the hetero atom(s) may beinterposed into the cyclic structure of the cyclic hydrocarbon group andthe monovalent hydrocarbon group; and M⁺ represents a monovalent cation.

When such a chemically amplified negative resist composition isemployed, acid diffusion can be effectively controlled by the action ofthe onium salt contained therein, so that when it is formed as a resistfilm and a pattern is formed, a pattern having good resolution andreduced in LER can be obtained.

Among these, the above-mentioned onium salt is preferably a compoundrepresented by the following general formula (1) or (2),

wherein R^(f) and M⁺ have the same meanings as defined above; Xrepresents O or CH₂; k¹ represents an integer of 0 to 2; and each Z¹,Z², Z³, Z⁴, Z⁵ and Z⁶ independently represent a hydrogen atom or alinear, branched or cyclic monovalent hydrocarbon group having 1 to 10carbon atoms which may be substituted by a hetero atom(s), and a heteroatom(s) may be interposed in the monovalent hydrocarbon group,

wherein R^(f), X, k¹, Z¹, Z², Z⁵, Z⁶ and M⁺ have the same meanings asdefined above.

When such a chemically amplified negative resist composition isemployed, resolution at the time of forming a pattern can be moreimproved, and preparing thereof becomes easy since the onium salt can bewell handled.

Among them, the resin preferably contains a repeating unit representedby the following general formula (3) or a repeating unit represented bythe following general formula (4), or both of them,

wherein each A and B represent a single bond or an alkylene group having1 to 10 carbon atoms which may contain an ether bond(s) in the chain ofthe alkylene group; each R¹ independently represents a hydrogen atom ora methyl group; each R^(X) independently represents a hydrogen atom oran alkyl group having 1 to 6 carbon atoms; X′ represents a hydrogenatom, a linear, branched or cyclic alkyl group having 1 to 20 carbonatoms, an alkoxyalkyl group having 2 to 20 carbon atoms, analkylthioalkyl group having 2 to 20 carbon atoms, a halogen atom, anitro group, a cyano group, a sulfinyl group or a sulfonyl group; Wrepresents an alkyl group having 1 to 20 carbon atoms or an acyl grouphaving 1 to 20 carbon atoms; “a” and “c” represent integers of 0 to 4;“b” represents an integer of 1 to 5; “d” represents an integer of 0 to5; each P and Q represent 0 or 1; and each “s” and “t” represent aninteger of 0 to 2.

When such a chemically amplified negative resist composition isemployed, adhesion to a workpiece when it is formed as a resist film canbe improved by the action of the above-mentioned repeating unit, andsolubility in an alkaline developer can be controlled.

Also, the above-mentioned resin preferably contains a repeating unitrepresented by the following general formula (5) or a repeating unitrepresented by the following general formula (6), or both of them,

wherein “f” represents an integer of 0 to 6; each R³ independentlyrepresents a hydrogen atom, an alkyl group having 1 to 6 carbon atomswhich may be substituted by a halogen atom(s), a primary or secondaryalkoxy group which may be substituted by a halogen atom(s) or analkylcarbonyloxy group having 1 to 7 carbon atoms which may besubstituted by a halogen atom(s); “g” represents an integer of 0 to 4;each R⁴ independently represents a hydrogen atom, an alkyl group having1 to 6 carbon atoms which may be substituted by a halogen atom(s), aprimary or secondary alkoxy group which may be substituted by a halogenatom(s) or an alkylcarbonyloxy group having 1 to 7 carbon atoms whichmay be substituted by a halogen atom(s).

When such a chemically amplified negative resist composition isemployed, etching selectivity to the workpiece at the time of forming apattern can be improved by the action of the above-mentioned repeatingunit.

Further, the above-mentioned chemically amplified negative resistcomposition preferably contains a crosslinking agent.

When such a chemically amplified negative resist composition isemployed, the crosslinking reaction of the resin in the exposed area canbe promoted at the time of forming a pattern, and a negative pattern canbe obtained more easily at the time of forming a pattern.

Further, the above-mentioned chemically amplified negative resistcomposition preferably contains one or more basic compounds representedby the following general formulae (7) to (9),

wherein each R¹² and R¹³ represent a linear, branched or cyclic alkylgroup having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbonatoms, an aralkyl group having 7 to 20 carbon atoms, a hydroxyalkylgroup having 2 to 20 carbon atoms, an alkoxyalkyl group having 2 to 20carbon atoms, an acyloxyalkyl group having 2 to 20 carbon atoms, or analkylthioalkyl group having 2 to 20 carbon atoms, or R¹² and R¹³ may bebonded to form a cyclic structure with the nitrogen atom to which theyare bonded; R¹⁴ represents a hydrogen atom, a linear, branched or cyclicalkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20carbon atoms, an aralkyl group having 7 to 20 carbon atoms, ahydroxyalkyl group having 2 to 20 carbon atoms, an alkoxyalkyl grouphaving 2 to 20 carbon atoms, an acyloxyalkyl group having 2 to 20 carbonatoms, an alkylthioalkyl group having 2 to 20 carbon atoms, or a halogenatom; R¹⁵ represents a single bond, a linear, branched or cyclicalkylene group having 1 to 20 carbon atoms, or an arylene group having 6to 20 carbon atoms; R¹⁶ represents a linear or branched alkylene grouphaving 2 to 20 carbon atoms which may be substituted, and the alkylenegroup may contain one or a plural number of a carbonyl group(s), anether group(s), an ester group(s) and a sulfide bond(s) betweencarbon-carbon bond of the alkylene group; and R¹⁷ represents a linear,branched or cyclic alkylene group having 1 to 20 carbon atoms, or anarylene group having 6 to 20 carbon atoms.

When such a chemically amplified negative resist composition isemployed, acid diffusion can be more effectively controlled, andgeneration of undercut of the pattern can be effectively suppressed.

The present invention also provides

a patterning process which comprises the steps of forming a resist filmon a workpiece using the above-mentioned chemically amplified negativeresist composition, irradiating a high energy beam to the resist film,and developing the resist film after irradiation using an alkalinedeveloper to obtain a resist pattern.

When such a patterning process is employed, acid diffusion at the timeof exposure can be effectively controlled by the action of the oniumsalt contained in the chemically amplified negative resist composition,so that a pattern with good resolution and reduced in LER can be formedonto the resist film.

At this time, EUV or an electron beam is preferably used as theabove-mentioned high-energy beam.

When such a patterning process is employed, finer pattern can be formedonto the resist film.

In addition, a substrate having a layer containing chromium at theoutermost layer is preferably used as the above-mentioned workpiece.

Further, a photomask blank is preferably used as the above-mentionedworkpiece.

Thus, when the patterning process of the present invention is employed,even when a workpiece (for example, photomask blank) having an outermostlayer which likely influences a pattern profile of the chemicallyamplified resist such as a layer at the outermost containing chromium,etc., is used, a resist film excellent in adhesion can be obtained, anda pattern reduced in line edge roughness can be formed by exposure.

The chemically amplified negative resist composition of the presentinvention can control acid diffusion effectively when the composition isexposed, and a pattern having extremely high resolution and reduced inLER can be obtained at the time of forming the pattern by the action ofthe onium salt contained therein. Also, when such a patterning processusing the chemically amplified negative resist composition is employed,a pattern having high resolution with reduced LER can be formed, so thatit can be suitably used for microprocessing technology, in particular,for an electron beam and EUV lithography technology.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, the present invention is explained in morespecifically.

The present inventors have studied to accomplish the above-mentionedproblems, and as a result, they have found that a pattern with less LERcan be obtained when an onium salt into which a fluorine atom or atrifluoromethyl group is introduced at an appropriate position of acarboxylic acid onium salt is added to a negative resist composition,whereby the present invention has been completed.

In the following, the present invention is explained in more detail.

Incidentally, in the following explanation, there exists an asymmetriccarbon depending on the structure represented by the chemical generalformula, so that an enantio isomer (enantiomer) or a diastereo isomer(diastereomer) can exist in some cases, and in such a case, theseisomers are represented by one general formula as a representative.These isomers may be used alone, or may be used as a mixture.

[Chemically Amplified Negative Resist Composition]

The present invention relates to

a chemically amplified negative resist composition comprising an oniumsalt represented by the following general formula (0-1), a resin whichbecomes alkali insoluble by an action of an acid and an acid generator,

wherein R^(f) represents a fluorine atom or a trifluoromethyl group; Yrepresents a cyclic hydrocarbon group having 3 to 30 carbon atoms, thehydrogen atom in the cyclic hydrocarbon group may be substituted by ahetero atom itself or a monovalent hydrocarbon group which may besubstituted by a hetero atom(s), and the hetero atom(s) may beinterposed into the cyclic structure of the cyclic hydrocarbon group andthe monovalent hydrocarbon group; and M⁺ represents a monovalent cation.

Preferred embodiment of the onium salt to be contained in the chemicallyamplified negative resist composition of the present invention is anonium salt represented by the following general formula (1) or (2),

wherein R^(f) and M⁺ have the same meanings as defined above; Xrepresents O or CH₂; k¹ represents an integer of 0 to 2; and each Z¹,Z², Z³, Z⁴, Z⁵ and Z⁶ independently represent a hydrogen atom or alinear, branched or cyclic monovalent hydrocarbon group having 1 to 10carbon atoms which may be substituted by a hetero atom(s), and a heteroatom(s) may be interposed in the monovalent hydrocarbon group,

wherein R^(f), X, k¹, Z¹, Z², Z⁵, Z⁶ and M⁺ have the same meanings asdefined above.

M⁺ in the above-mentioned general formula (0-1), (1) and (2) representsa monovalent cation. The monovalent cation is not particularly limited,and may be mentioned a sulfonium cation represented by the followinggeneral formula (10),

wherein each R⁵, R⁶ and R⁷ independently represent a substituted orunsubstituted, linear or branched alkyl group, alkenyl group or oxoalkylgroup each having 1 to 10 carbon atoms, or a substituted orunsubstituted aryl group, aralkyl group or aryloxoalkyl group eachhaving 6 to 18 carbon atoms, and two or more of R⁵, R⁶ and R⁷ may bebonded to each other to form a ring with the sulfur atom in the formula.

The above-mentioned alkyl group may be specifically mentioned a methylgroup, an ethyl group, a propyl group, an isopropyl group, a n-butylgroup, a sec-butyl group, a tert-butyl group, a pentyl group, a hexylgroup, a heptyl group, an octyl group, a cyclopentyl group, a cyclohexylgroup, a cycloheptyl group, a cyclopropylmethyl group, a4-methylcyclohexyl group, a cyclohexylmethyl group, a norbornyl group,an adamantyl group, etc. The alkenyl group may be mentioned a vinylgroup, an allyl group, a propenyl group, a butenyl group, a hexenylgroup, a cyclohexenyl group, etc. The oxoalkyl group may be mentioned a2-oxocyclopentyl group, a 2-oxocyclohexyl group, a 2-oxopropyl group, a2-oxoethyl group, a 2-cyclopentyl-2-oxoethyl group, a2-cyclohexyl-2-oxoethyl group, a 2-(4-methylcyclohexyl)-2-oxoethylgroup, etc.

In addition, the aryl group may be mentioned a phenyl group, a naphthylgroup, a thienyl group, etc., an alkoxyphenyl group such as a4-hydroxyphenyl group, a 4-methoxyphenyl group, a 3-methoxyphenyl group,a 2-methoxyphenyl group, a 4-ethoxyphenyl group, a 4-tert-butoxyphenylgroup, a 3-tert-butoxyphenyl group, etc., an alkylphenyl group such as a2-methylphenyl group, a 3-methylphenyl group, a 4-methylphenyl group, a4-ethylphenyl group, a 4-tert-butylphenyl group, a 4-n-butylphenylgroup, a 2,4-dimethylphenyl group, etc., an alkylnaphthyl group such asa methylnaphthyl group, an ethylnaphthyl group, etc., an alkoxynaphthylgroup such as a methoxynaphthyl group, an ethoxynaphthyl group, etc., adialkylnaphthyl group such as a dimethylnaphthyl group, adiethylnaphthyl group, etc., and a dialkoxynaphthyl group such as adimethoxynaphthyl group, a diethoxynaphthyl group, etc. The aralkylgroup may be mentioned a benzyl group, a 1-phenylethyl group, a2-phenylethyl group, etc. The aryloxoalkyl group may be mentioned a2-aryl-2-oxoethyl group such as a 2-phenyl-2-oxoethyl group, a2-(l-naphthyl)-2-oxoethyl group, a 2-(2-naphthyl)-2-oxoethyl group, etc.

Also, when two or more of R⁵, R⁶ and R⁷ are bonded to each other to forma ring with the sulfur atom in the formula, the group forming thesecyclic structures may be mentioned a divalent organic group such as1,4-butylene, 3-oxa-1,5-pentylene, etc. Further, there may be mentionedan aryl group having a polymerizable substituent(s) such as anacryloyloxy group, a methacryloyloxy group, etc., as a substituent(s),and specifically mentioned a 4-acryloyloxyphenyl group, a4-methacryloyloxyphenyl group, a 4-acryloyloxy-3,5-dimethylphenyl group,a 4-methacryloyloxy-3,5-dimethylphenyl group, a 4-vinyloxyphenyl group,a 4-vinylphenyl group, etc.

The above-mentioned sulfonium cation may be specifically mentionedtriphenyl sulfonium, 4-hydroxy-phenyldiphenyl sulfonium,bis(4-hydroxyphenyl)phenyl sulfonium, tris(4-hydroxyphenyl)sulfonium,4-tert-butoxyphenyldiphenyl sulfonium, bis(4-tert-butoxyphenyl)phenylsulfonium, tris(4-tert-butoxyphenyl)sulfonium,3-tert-butoxyphenyldiphenyl sulfonium, bis(3-tert-butoxyphenyl)phenylsulfonium, tris(3-tert-butoxyphenyl)sulfonium,3,4-di-tert-butoxyphenyldiphenyl sulfonium,bis(3,4-di-tert-butoxyphenyl)phenyl sulfonium,tris(3,4-di-tert-butoxyphenyl)sulfonium,diphenyl(4-thiophenoxyphenyl)sulfonium,4-tert-butoxycarbonylmethyloxyphenyldiphenyl sulfonium,tris(4-tert-butoxycarbonylmethyloxyphenyl)sulfonium,(4-tert-butoxyphenyl)bis(4-dimethylaminophenyl)sulfonium,tris(4-dimethylaminophenyl)sulfonium, 2-naphthyldiphenyl sulfonium,(4-hydroxy-3,5-dimethylphenyl)diphenyl sulfonium,(4-n-hexyloxy-3,5-dimethylphenyl)diphenyl sulfonium,dimethyl(2-naphthyl)sulfonium, 4-hydroxyphenyldimethyl sulfonium,4-methoxyphenyldimethyl sulfonium, trimethyl sulfonium,2-oxocyclohexylcyclohexylmethyl sulfonium, trinaphthyl sulfonium,tribenzyl sulfonium, diphenylmethyl sulfonium, dimethylphenyl sulfonium,5-phenyldibenzothiophenium, 10-phenylphenoxathiinium,2-oxo-2-phenylethylthiacyclopentanium, diphenyl2-thienyl sulfonium,4-n-butoxynaphthyl-1-thiacyclopentanium,2-n-butoxynaphthyl-1-thiacyclopentanium,4-methoxynaphthyl-1-thiacyclopentanium,2-methoxynaphthyl-1-thiacyclopentanium, 4-methylphenyldiphenylsulfonium, 4-ethylphenyldiphenyl sulfonium, 4-tert-butylphenyldiphenylsulfonium, 4-cyclo-hexylphenyldiphenyl sulfonium,4-n-hexylphenyldiphenyl sulfonium, 4-n-octylphenyldiphenyl sulfonium,4-methoxy-phenyldiphenyl sulfonium, 4-ethoxyphenyldiphenyl sulfonium,4-tert-butoxyphenyldiphenyl sulfonium, 4-cyclohexyloxyphenyldiphenylsulfonium, 4-n-hexyloxyphenyldiphenyl sulfonium,4-n-octyloxyphenyldiphenyl sulfonium, 4-dodecyl-oxyphenyldiphenylsulfonium, 4-trifluoromethylphenyl-diphenyl sulfonium,4-trifluoromethyloxyphenyldiphenyl sulfonium,4-tert-butoxycarbonylmethyloxyphenyldiphenyl sulfonium,4-methacryloyloxyphenyldiphenyl sulfonium, 4-acryloyloxyphenyldiphenylsulfonium, (4-n-hexyloxy-3,5-dimethylphenyl)diphenylsulfonium,(4-methacryloyloxy-3,5-dimethylphenyl)diphenyl sulfonium,(4-acryloyloxy-3,5-dimethylphenyl)diphenylsulfonium, etc.

It is more preferably mentioned triphenyl sulfonium,4-tert-butylphenyldiphenyl sulfonium, 4-tert-butoxyphenyldiphenylsulfonium, tris(4-tert-butylphenyl)sulfonium,4-tert-butoxycarbonylmethyloxyphenyldiphenyl sulfonium,4-methacryloyloxyphenyldiphenyl sulfonium, 4-acryloyloxyphenyldiphenylsulfonium, 4-methacryloyloxyphenyldimethyl sulfonium,4-acryloyloxyphenyldimethyl sulfonium,(4-methacryloyloxy-3,5-dimethylphenyl)diphenyl sulfonium,(4-acryloyloxy-3,5-dimethylphenyl)diphenylsulfonium, etc.

Also, the monovalent cation represented by M⁺ in the above-mentionedgeneral formulae (0-1), (1) and (2) may be mentioned, other than thesulfonium cation, an iodonium cation and an ammonium cation, etc.

More specific iodonium cation may be exemplified by diphenyliodonium,bis(4-methylphenyl)iodonium, bis(4-(1,1-dimethylethyl)phenyl)iodonium,bis(4-(1,1-dimethylpropyl)phenyl)iodonium,(4-(1,1-dimethylethoxy)phenyl)phenyliodonium, etc., and the ammoniumcation may be exemplified by a tertiary ammonium salt such as a salt oftrimethylammonium, triethylammonium, tributylammonium,N,N-dimethyl-anilinium, etc., or a quaternary ammonium salt such as asalt of tetramethylammonium, tetraethylammonium, tetrabutylammonium,etc.

In the above-mentioned general formulae (1) and (2), each Z¹, Z², Z³,Z⁴, Z⁵ and Z⁶ independently represent a hydrogen atom or a linear,branched or cyclic monovalent hydrocarbon group having 1 to 10 carbonatoms which may be substituted by a hetero atom(s), and a hetero atom(s)may be interposed in the monovalent hydrocarbon group. Such a monovalenthydrocarbon group may be specifically exemplified by a methyl group, anethyl group, a propyl group, an isopropyl group, a n-butyl group, asec-butyl group, a tert-butyl group, a tert-amyl group, a n-pentylgroup, a n-hexyl group, a n-octyl group, a n-nonyl group, a n-decylgroup, a cyclopentyl group, a cyclohexyl group, a 2-ethylhexyl group, acyclopentylmethyl group, a cyclopentylethyl group, a cyclopentylbutylgroup, a cyclohexylmethyl group, a cyclohexylethyl group, acyclohexylbutyl group, a norbornyl group, an oxanorbornyl group, atricyclo[5.2.1.0^(2,6)]decanyl group, an adamantyl group, etc. Also, apart of the hydrogen atom(s) of these groups may be substituted by ahetero atom(s) such as an oxygen atom, a sulfur atom, a nitrogen atom, ahalogen atom, etc., or a hetero atom(s) such as an oxygen atom, a sulfuratom, a nitrogen atom, etc., may be interposed therebetween. That is,they may form or may be interposed by a hydroxyl group, a cyano group, acarbonyl group, an ether bond, an ester bond, a sulfonate ester bond, acarbonate bond, a lactone ring, a sultone ring, a carboxylic acidanhydride, a haloalkyl group, etc.

Preferred specific examples of the carboxylic acid anion in theabove-mentioned general formula (1) or (2) are shown below.

A method for obtaining the onium salt represented by the above-mentionedgeneral formula (2) is exemplified by the following reaction scheme, butthe invention is not limited by these.

wherein R^(f), X, k¹, Z¹, Z², Z⁵, Z⁶ and M⁺ have the same meanings asdefined above; and L⁻ represents a halide ion or methyl sulfate ion.

The step (i) in the above-mentioned scheme is a step to give acarboxylic acid (13) by the Diels-Alder reaction of a diene (11) and afluorinated acrylic acid (12). The reaction may be preferably carriedout without solvent or in a solvent such as methylene chloride, toluene,hexane, diethyl ether, tetrahydrofuran, acetonitrile, etc., by mixingthe diene (11) and the fluorinated acrylic acid (12), under cooling orheating, if necessary.

The step (ii) is a step to convert the carboxylic acid (13) to a sodiumsalt (14). The solvent which can be used for the reaction may bementioned water, ethers such as tetrahydrofuran, diethyl ether,diisopropyl ether, di-n-butyl ether, 1,4-dioxane, etc., hydrocarbonssuch as n-hexane, n-heptane, benzene, toluene, xylene, etc., aproticpolar solvents such as acetonitrile, dimethylsulfoxide (DMSO),N,N-dimethylformamide (DMF), etc., chlorinated organic solvents such asmethylene chloride, chloroform, carbon tetrachloride, etc. Thesesolvents may be used by optionally selecting depending on the reactionconditions, and may be used one kind alone or two or more kinds inadmixture. The reaction may be preferably carried out in theabove-mentioned solvent by mixing the carboxylic acid (13) and sodiumhydrogen carbonate, under cooling or heating, if necessary.

The step (iii) is a step of obtaining an objective onium salt (2) by anion-exchange reaction of the sodium salt of a carboxylic acid (14) andan onium salt (15). The solvent which can be used for the reaction maybe mentioned water, ethers such as tetrahydrofuran, diethyl ether,diisopropyl ether, di-n-butyl ether, 1,4-dioxane, etc., hydrocarbonssuch as n-hexane, n-heptane, benzene, toluene, xylene, etc., aproticpolar solvents such as acetonitrile, dimethylsulfoxide (DMSO),N,N-dimethylformamide (DMF), etc., chlorinated organic solvents such asmethylene chloride, chloroform, carbon tetrachloride, etc. Thesesolvents may be used by optionally selecting depending on the reactionconditions, and may be used one kind alone or two or more kinds inadmixture. The reaction may be preferably carried out in theabove-mentioned solvent by mixing the carboxylic acid salt (14) and theonium salt (15), under cooling or heating, if necessary. The objectiveonium salt (2) can be obtained from the reaction mixture by the usualpost-treatment of the aqueous system (aqueous work-up), and can bepurified by the conventional method such as recrystallization,chromatography, etc., if necessary.

A method for obtaining the onium salt represented by the general formula(1′) in which Z³ and Z⁴ in the above-mentioned general formula (1) arehydrogen atoms is exemplified by the following reaction scheme, but theinvention is not limited by these,

wherein R^(f), X, k¹, Z¹, Z², Z⁵, Z⁶, M⁺ and L⁻ have the same meaningsas defined above.

The above-mentioned step (iv) is the same as the step (i) in the schemefor obtaining the onium salt represented by the above-mentioned generalformula (2).

The above-mentioned step (v) is a step to obtain a carboxylic acid (16)by hydrogenating the double bond of the carboxylic acid (13) byhydrogenation reaction. The reaction may be preferably carried outwithout solvent or in a solvent such as methylene chloride, methanol,toluene, hexane, diethyl ether, tetrahydrofuran, acetonitrile, etc., bymixing a palladium catalyst and the carboxylic acid (13), and stirringthe same under hydrogen atmosphere. In addition, it may be carried outunder cooling or heating, if necessary.

The above-mentioned steps (vi) and (vii) are the same as the step (iii)and the step (iv), respectively, in the scheme for obtaining the oniumsalt represented by the above-mentioned genreal formula (2). That is,the step (vi) is a step of converting the carboxylic acid (16) to asodium salt (17), and the step (vii) is a step of obtaining an objectiveonium salt (1′) by an ion-exchange reaction of the sodium salt (17) andan onium salt (15).

Among the above-mentioned schemes, the onium salt (15) to be used in theion-exchange reaction with the carboxylic acid salts (14, 16) is notparticularly limited, and may be exemplified by a sulfonium salt, aniodonium salt, an ammonium salt, etc., which can give theabove-mentioned sulfonium cation, iodonium cation or ammonium cation.

When the onium salt represented by the above-mentioned general formula(0-1) of the present invention, in particular, the onium saltrepresented by the above-mentioned general formula (1) or (2) isformulated in the chemically amplified resist composition, a strong acid(sulfonic acid, etc.) generated from the other photoacid generator byexposure is exchanged with the onium salt of the present invention, toform a weak acid and a strong acid=onium salt whereby exchanging from astrong acid (sulfonic acid, etc.) having high acidity to a weak acid(carboxylic acid). It is to suppress the acid decomposition reaction ofthe acid-labile group as a result, and to make the acid diffusiondistance small (to control), whereby it apparently acts as an aciddiffusion controlling agent. The onium salt of the present inventioncontains a fluorine atom(s) at the α-position of the carboxyl group or afluoroalkyl group so that acidity thereof is considered to be increasedas compared with the carboxylic acid the α-position of which is notsubstituted. As a result, the difference of a pKa thereof from that ofthe strong acid such as sulfonic acid, etc., becomes small, so that arapid exchange reaction is considered to be easily caused, and this isconsidered to be contributed to lower the roughness such as LER.

Acidity of the acid generated from the onium salt preferably has a pKain the range of 1.5 to 4.0, more preferably in the range of 1.5 to 3.5.If the pKa is 1.5 or more, there is no fear of increasing the aciditythan required, and it can function sufficiently as the acid diffusioncontrolling agent. On the other hand, if the pKa is 4.0 or less, thedifference in the pKa thereof from that of the acid generated from thephotoacid generator is not so large, and it does not completely trap theacid, so that the above-mentioned sufficient effect of reducingroughness by the exchange reaction of the acid and the onium salt can beobtained.

Also, the onium salt represented by the above-mentioned general formula(1) or (2) of the present invention contains a bulky alicyclicstructure, so that it can be considered that migration and diffusion ofthe strong acid can be more effectively controlled. Incidentally, theonium salt represented by the above-mentioned general formula (1) or (2)of the present invention has sufficient lipophilicity so that producingand handling thereof are easy.

When it is such an onium salt, it can be suitably used as a material ofthe chemically amplified negative resist composition mentioned later.

The chemically amplified negative resist composition of the presentinvention is a composition containing the onium salt represented by theabove-mentioned general formula (0-1), (1), or (2). The chemicallyamplified negative resist composition of the present invention is acomposition containing, in addition to the above-mentioned onium salt, abase resin and an acid generator, and further preferably a compositioncontaining a crosslinking agent, a basic compound and an organicsolvent. When the chemically amplified negative resist composition ofthe present invention is to be prepared, a resin which becomes alkaliinsoluble by an action of an acid is used as the base resin. The resinwhich becomes alkali insoluble by an action of an acid is notparticularly limited, and preferably used is a resin which becomes ahigher molecular weight in which the resins form cross-linked structureby the action of an acid, or a resin which becomes a higher molecularweight by reacting with a crosslinking agent mentioned later by theaction of an acid.

The above-mentioned base resin is preferably a resin containing arepeating unit represented by the following general formula (3) or arepeating unit represented by the following general formula (4), or bothof them,

wherein each A and B represent a single bond or an alkylene group having1 to 10 carbon atoms which may contain an ether bond(s) in the chain ofthe alkylene group; each R¹ independently represents a hydrogen atom ora methyl group; each R^(X) independently represents a hydrogen atom oran alkyl group having 1 to 6 carbon atoms; X′ represents a hydrogenatom, a linear, branched or cyclic alkyl group having 1 to 20 carbonatoms, an alkoxyalkyl group having 2 to 20 carbon atoms, analkylthioalkyl group having 2 to 20 carbon atoms, a halogen atom, anitro group, a cyano group, a sulfinyl group or a sulfonyl group; Wrepresents an alkyl group having 1 to 20 carbon atoms or an acyl grouphaving 1 to 20 carbon atoms; “a” and “c” represent integers of 0 to 4;“b” represents an integer of 1 to 5; “d” represents an integer of 0 to5; each P and Q represent 0 or 1; and each “s” and “t” represent aninteger of 0 to 2.

The repeating unit represented by the above-mentioned general formula(3) is a repeating unit which provides etching resistance as well asadhesion to the substrate and solubility to the alkaline developer. Thisrepeating unit has already been used in many resist compositions for KrFexcimer laser or resist compositions for an electron beam including theabove-mentioned prior art technologies.

In the above-mentioned general formula (3), A represents a single bondor an alkylene group having 1 to 10 carbon atoms which may contain anether bond(s) in the chain of the alkylene group.

Examples of the preferred alkylene group may be mentioned a methylenegroup, an ethylene group, a propylene group, a butylene group, apentylene group, a hexylene group and structural isomers with carbonskeleton having a branched or cyclic structure, etc., and when itcontains an ether bond, when P in the general formula (3) is 1, it maybe at any position except for the position between the carbon at theα-position to the ester oxygen and the carbon at the β-position to thesame. Also, when P is 0, the atom bonded to the main chain is an etheroxygen, and the second ether bond may be at any position except for theposition between the carbon at the α-position to the ether oxygen andthe carbon at the β-position to the same. If the carbon number of theabove-mentioned alkylene group is 10 or less, it is preferred sincesolubility to the alkaline developer can be obtained sufficiently.

Each R^(X) independently represents a hydrogen atom or an alkyl grouphaving 1 to 6 carbon atoms; and preferred examples of the alkyl grouphaving 1 to 6 carbon atoms may be mentioned a methyl group, an ethylgroup, a propyl group, an isopropyl group, a butyl group, a pentylgroup, a hexyl group and structural isomers with carbon skeleton havinga branched or cyclic structure. If the carbon number is 6 or less, it ispreferred since solubility to the alkaline developer can be sufficientlyobtained.

In the above-mentioned general formula (3), “a” represents an integer of0 to 4 and “b” represents an integer of 1 to 5, and when “s” represents0, preferably “a” represents an integer of 0 to 3 and “b” represents aninteger of 1 to 3, when “s” represents 1 or 2, preferably “a” representsan integer of 0 to 4 and “b” represents an integer of 1 to 5.

Further, “s” represents an integer of 0 to 2, and when “s” represents 0,it shows a benzene skeleton, when “s” represents 1, it shows anaphthalene skeleton, and when “s” represents 2, it shows an anthraceneskeleton, respectively.

Among the repeating units represented by the above-mentioned generalformula (3), when P represents 0 and A is a single bond, that is, thearomatic ring is directly bonded to the main chain of the polymer, i.e.,there is no linker, the repeating unit is a unit derived from a monomerhaving a substituted or unsubstituted vinyl group at its 1-position thatis bonded to an aromatic ring substituted with a hydroxyl group, whichis represented by a hydroxystyrene unit, and preferred specific examplesthereof may be mentioned 3-hydroxystyrene, 4-hydroxystyrene,5-hydroxy-2-vinylnaphthalene, 6-hydroxy-2-vinylnaphthalene, etc.

Also, the repeating unit when P is 1, that is, when it has an esterskeleton as the linker, is a vinyl monomer unit substituted with acarbonyl group, which is represented by a (meth)acrylate ester.

Preferred specific examples of the general formula (3) in the case ofhaving a linker (—CO—O-A-) derived from a (meth)acrylate ester are shownbelow.

The repeating unit represented by the above-mentioned general formula(4) is a repeating unit which provides etching resistance as well ascontrols solubility to the alkaline developer. This repeating unit hasalso already been used as in the above-mentioned general formula (3) inmany resist compositions for KrF excimer laser or resist compositionsfor an electron beam including the above-mentioned prior arttechnologies.

In the above-mentioned general formula (4), B is a single bond or analkylene group having 1 to 10 carbon atoms which may contain an etherbond(s) in the chain of the alkylene group.

Preferred examples of the alkylene group may be mentioned a methylenegroup, an ethylene group, a propylene group, a butylene group, apentylene group, a hexylene group and structural isomers of the carbonskeleton having a branched or a cyclic structure, etc., and when anether bond is contained therein, and when Q in the general formula (4)is 1, it may be at any position except for the position between thecarbon at the α-position to the ester oxygen and the carbon at theβ-position to the same. Also, when Q represents 0, the atom bonded tothe main chain is an ether oxygen, and the second ether bond may be atany position except for the position between the carbon at theα-position to the ether oxygen and the carbon at the β-position to thesame. Incidentally, if the carbon number of the above-mentioned alkylenegroup is 10 or less, it is preferred since solubility to the alkalinedeveloper can be sufficiently obtained.

X′ shown in the above-mentioned general formula (4) represents ahydrogen atom, a linear, branched or cyclic alkyl group having 1 to 20carbon atoms, an alkoxyalkyl group having 2 to 20, preferably 2 to 10carbon atoms, an alkylthioalkyl group having 2 to 20, preferably 2 to 10carbon atoms, a halogen atom, a nitro group, a cyano group, a sulfinylgroup or a sulfonyl group. More specific preferred substituents may bementioned a hydrogen atom, a halogen atom such as a chlorine atom, abromine atom and an iodine atom, an alkyl group such as a methyl group,an ethyl group, a propyl group, a butyl group, a pentyl group, a hexylgroup and structural isomers thereof, a cyclopentyl group, a cyclohexylgroup, etc. If the carbon number thereof is 20 or less, an effect ofcontrolling and adjusting solubility of the base resin to an alkalinedeveloper (mainly a lowering effect) can be made suitable, andgeneration of scum (development defects) can be suppressed. Also, amongthe preferred substituents as mentioned above, particularly, as asubstituent which can be prepared as a monomer easily and can be usedusefully, there may be mentioned a hydrogen atom, a chlorine atom, abromine atom, an iodine atom, a methyl group and an ethyl group.

Also, W shown in the above-mentioned general formula (4) represents analkyl group having 1 to 20 carbon atoms, preferably 1 to 6 carbon atomsor an acyl group having 1 to 20 carbon atoms, preferably 2 to 7 carbonatoms, and when W is an alkyl group, OW is an alkoxy group, and W is anacyl group, OW is an acyloxy group. Preferred alkoxy group may bementioned a methoxy group, an ethoxy group, a propoxy group, a butoxygroup, a pentyloxy group, a hexyloxy group and structural isomers at thehydrocarbon moiety thereof, a cyclopentyloxy group, a cyclohexyloxygroup, etc., and a methoxy group and an ethoxy group can be particularlyutilized usefully. Also, the acyloxy group can be easily introducedtherein by the chemical modification method even after polymerization ofthe polymer, and it can be advantageously used for fine adjustment ofsolubility of the base resin to the alkaline developer. In this case, amethylcarbonyloxy group, an ethylcarbonyloxy group, a propylcarbonyloxygroup, a butylcarbonyloxy group, a pentylcarbonyloxy group, ahexylcarbonyloxy group and structural isomers thereof, acyclopentylcarbonyloxy group, a cyclohexylcarbonyloxy group, abenzoyloxy group, etc., can be preferably used.

In the above-mentioned general formula (4), “c” represents an integer of0 to 4 and “d” represents an integer of 0 to 5, when “t” represents 0,preferably “c” represents an integer of 0 to 3 and “d” represents aninteger of 0 to 3, and when “t” represents 1 or 2, preferably “c”represents an integer of 0 to 4 and “d” represents an integer of 0 to 5.

Further, “t” represents an integer of 0 to 2, when “t” represents 0, itshows a benzene skeleton, when “t” represents 1, it shows a naphthaleneskeleton, and when “t” represents 2, it shows an anthracene skeleton,respectively.

Among the basic skeleton of the repeating units represented by theabove-mentioned general formula (4), when Q represents 0 and B is asingle bond, that is, the aromatic ring is directly bonded to the mainchain of the polymer, i.e., there is no linker, the basic skeleton ofthe repeating unit is a unit derived from a monomer substituted with theabove-mentioned X′ and/or OW, having a substituted or unsubstitutedvinyl group at its 1-position that is bonded to the aromatic ring, whichis represented by the styrene skeleton, and preferred specific examplesof the basic skeletons may be mentioned styrene, 4-chlorostyrene,4-methyistyrene, 4-methoxystyrene, 4-bromostyrene,2-hydroxypropylstyrene, 2-vinylnaphthalene, 3-vinylnaphthalene, etc.

Also, the repeating unit when Q represents 1, that is, it has an esterskeleton as the linker, is a vinyl monomer unit substituted with acarbonyl group, which is represented by a (meth)acrylate ester.

Preferred specific examples regarding the basic skeleton of the generalformula (4) in the case of having a linker (—CO—O—B—) derived from a(meth)acrylate ester are shown below.

wherein Me represents a methyl group.

It is also preferred that the above-mentioned base resin furthercontains a repeating unit represented by the following general formula(5) or a repeating unit represented by the following general formula(6), or both of them, as the main constitutional unit of the polymer,

wherein “f” represents an integer of 0 to 6; each R³ independentlyrepresents a hydrogen atom, an alkyl group having 1 to 6 carbon atomswhich may be substituted by a halogen atom(s), a primary or secondaryalkoxy group which may be substituted by a halogen atom(s) or analkylcarbonyloxy group having 1 to 7 carbon atoms which may besubstituted by a halogen atom(s); “g” represents an integer of 0 to 4;each R⁴ independently represents a hydrogen atom, an alkyl group having1 to 6 carbon atoms which may be substituted by a halogen atom(s), aprimary or secondary alkoxy group which may be substituted by a halogenatom(s) or an alkylcarbonyloxy group having 1 to 7 carbon atoms whichmay be substituted by a halogen atom(s).

When these repeating units (at least one of the repeating unitrepresented by the above-mentioned general formula (5) and the repeatingunit represented by the above-mentioned general formula (6)) are used asa constitutional component(s), it is possible to obtain an effect ofheightening resistance to electron beam irradiation at the time ofetching or pattern inspection due to addition of the cyclic structure tothe main chain, in addition to etching resistance due to the aromaticring.

The units which improve etching resistance by providing a cyclicstructure to the main chain represented by the above-mentioned generalformula (5) and the general formula (6) may be used one kind alone or aplural kinds of the units in combination, and to obtain the effect thatetching resistance is to be improved, it is preferably introduced in anamount of 5 mole % or more based on the amount of the whole monomer unitconstituting the base resin.

The above-mentioned base resin to be used in the chemically amplifiednegative resist composition of the present invention preferablycomprises the above-mentioned general formulae (3) and (4) as the mainconstitutional units, and further the units of the general formulae (5)and (6) which can be introduced, in an amount of 60 mole % or more basedon the amount of the whole monomer unit constituting the base resinwhereby the characteristics required as the chemically amplifiednegative resist composition of the present invention can be certainlyobtained, more preferably 70 mole % or more, particularly preferably 85mole % or more.

When the base resin comprises the repeating units(s) selected from theunits represented by the general formulae (3) to (6) as the wholeconstitutional unit, both high etching resistance and excellentresolution can be attained. As the repeating units other than the unitsrepresented by the general formulae (3) to (6), there may be used a(meth)acrylate ester unit protected by the conventionally usedacid-labile group, or a (meth)acrylate ester unit having an adhesiongroup such as a lactone structure, etc. Fine adjustment of thecharacteristics of the resist film may be carried out by these otherrepeating unit(s), but these unit(s) may not be contained.

The base resin to be used in the resist composition of the presentinvention can be obtained by copolymerizing the respective monomers bycombining protection and deprotection reaction, depending on necessity,according to the conventionally known method. The copolymerizationreaction is not particularly limited, and preferably radicalpolymerization, or anion polymerization. These methods can be referredto International Patent Laid-Open Publication No. 2006/121096, JapanesePatent Laid-Open Publication No. 2008-102383, Japanese Patent Laid-OpenPublication No. 2008-304590 and Japanese Patent Laid-Open PublicationNo. 2004-115630.

A preferred molecular weight of the above-mentioned base resin to beused in the above-mentioned chemically amplified negative resistcomposition is preferably a weight average molecular weight of 2,000 to50,000, more preferably 3,000 to 20,000 when the molecular weight ismeasured, as a general method, by gel permeation chromatography (GPC)using polystyrenes as standard samples. If the weight average molecularweight is 2,000 or more, there is no fear of causing the phenomenon thatthe profile of the pattern becomes rounding to lower the resolution, aswell as the line edge roughness is deteriorated as has conventionallybeen known. On the other hand, if the molecular weight becomes largerthan required, line edge roughness tends to be increased while itdepends on the pattern to be resolved, so that the molecular weight ispreferably controlled to 50,000 or less, in particular, when a patternwith a pattern line width of 100 nm or less is to be formed, it ispreferably controlled to 20,000 or less.

Incidentally, measurement of the GPC can be carried out by usingtetrahydrofuran (THF) solvent generally used.

Further, in the base resin to be used in the above-mentioned chemicallyamplified negative resist composition of the present invention, themolecular weight distribution (Mw/Mn) is preferably narrow distributionof 1.0 to 2.0, particularly preferably 1.0 to 1.8. When it is narrowdistribution as mentioned above, no foreign substance is generated onthe pattern or the profile of the pattern is not deteriorated afterdevelopment.

In the chemically amplified negative resist composition of the presentinvention, an acid generator is contained for making the negative resistcomposition to be used in the patterning process of the presentinvention function. As such an acid generator, for example, a compound(a photoacid generator) which generates an acid in response to activebeam or irradiation beam may be contained. As the component of thephotoacid generator, any compound may be used as long as it is acompound generating an acid by irradiation of a high-energy beam.Suitable photoacid generator may be mentioned a sulfonium salt, aniodonium salt, sulfonyldiazomethane, N-sulfonyloxyimide, anoxime-O-sulfonate type acid generator, etc. These may be used singly ortwo or more kinds in admixture.

Specific examples of such an acid generator are disclosed in theparagraphs [0122] to [0142] of Japanese Patent Laid-Open Publication No.2008-111103.

Among the specific examples of the above-mentioned acid generator, anarylsulfonate type photoacid generator is preferred to generate an acidwith suitable acid strength for reacting the crosslinking agent and thepolymer mentioned later. Also, for obtaining an effect to improve LER bycausing an exchange reaction by combining a generating acid and theonium salt contained in the resist composition of the present invention,a pKa of the acid generating from the photoacid generator is preferablyin the range of −3.0 to 1.5, more preferably in the range of −1.0 to1.5.

Into the chemically amplified negative resist composition of the presentinvention, a crosslinking agent may be further formulated to form orstrengthen the cross-linked structure of the base resin. Specificexamples of the crosslinking agent which may be used in the presentinvention may be enumerated by a melamine compound that is substitutedby at least one group selected from a methylol group, an alkoxymethylgroup and an acyloxymethyl group; a guanamine compound, a glycolurilcompound, a urea compound, an epoxy compound, an isocyanate compound, anazide compound and a compound containing a double bond such as analkenyl ether group, etc. These may be used as an additive, or may beintroduced into the polymer side chain as a pendant group. Also, acompound containing a hydroxyl group may be also used as thecrosslinking agent.

Among the specific examples of the above-mentioned crosslinking agents,when the epoxy compound is further exemplified, there may be exemplifiedby tris(2,3-epoxypropyl)isocyanurate, trimethylolmethane triglycidylether, trimethylolpropane triglycidyl ether, triethylolethanetriglycidyl ether, etc.

When the melamine compound is specifically exemplified, there may bementioned hexamethylolmelamine, hexamethoxymethylmelamine, a compound inwhich 1 to 6 methylol groups of the hexamethylolmelamine is/aremethoxymethylated or a mixture thereof, hexamethoxyethylmelamine,hexaacyloxymethylmelamine, and a compound in which 1 to 6 methylolgroups of the hexamethylolmelamine is/are acyloxymethylated or a mixturethereof.

The guanamine compound may be mentioned tetramethylol guanamine,tetramethoxymethyl guanamine, a compound in which 1 to 4 methylol groupsof the tetramethylol guanamine is/are methoxymethylated or a mixturethereof, tetramethoxyethyl guanamine, tetraacyloxy guanamine, and acompound in which 1 to 4 methylol groups of the tetramethylol guanamineis/are acyloxymethylated or a mixture thereof.

The glycoluril compound may be mentioned tetramethylol glycoluril,tetramethoxy glycoluril, tetramethoxy methyl glycoluril, a compound inwhich 1 to 4 methylol groups of the tetramethylol glycoluril is/aremethoxymethylated or a mixture thereof, and a compound in which 1 to 4methylol groups of the tetramethylol glycoluril is/are acyloxymethylatedor a mixture thereof.

The urea compound may be mentioned tetramethylol urea,tetramethoxymethyl urea, a compound in which 1 to 4 methylol group ofthe tetramethylol urea is/are methoxymethylated or a mixture thereof,and tetramethoxyethyl urea, etc.

The isocyanate compound may be mentioned tolylene diisocyanate,diphenylmethane diisocyanate, hexamethylene diisocyanate and cyclohexanediisocyanate, etc.

The azide compound may be mentioned 1,1′-biphenyl-4,4′-bisazide,4,4′-methylidene bisazide and 4,4′-oxybisazide.

The compound containing an alkenyl ether group may be mentioned ethyleneglycol divinyl ether, triethylene glycol divinyl ether, 1,2-propanedioldivinyl ether, 1,4-butanediol divinyl ether, tetramethylene glycoldivinyl ether, neopentyl glycol divinyl ether,trimethylolpropanetrivinyl ether, hexanediol divinyl ether,1,4-cyclohexanediol divinyl ether, pentaerythritol trivinyl ether,pentaerythritol tetravinyl ether, sorbitol tetravinyl ether, sorbitolpentavinyl ether, trimethylolpropanetrivinyl ether, etc.

A formulation amount of the crosslinking agent is preferably 0 to 50parts by mass, more preferably 5 to 50 parts by mass, further preferably10 to 30 parts by mass, based on 100 parts by mass of the base resin,and it may be used singly or two or more kinds in admixture. If theamount is 5 parts by mass or more, sufficient improvement in resolutioncan be obtained, while if it is 30 parts by mass or less, there islittle possibility to lower the resolution by adhesion between thepatterns.

In the resist composition of the present invention, an amine compoundhaving a carboxyl group but not having a hydrogen atom covalently bondedto a nitrogen atom of a basic center may be contained as a basiccompound.

In patterning, the problem of the so-called substrate dependency of thepattern, in which the profile is changed in the vicinity of thesubstrate depending on a material of the workpiece, and a small changein the profile becomes the problem accompanied by miniaturization of theobjective pattern. In particular, when a photomask blank is to beprocessed, if patterning is carried out using the chemically amplifiednegative resist composition on chromium oxynitride which is a materialat the outermost surface of the photomask blank, there was a case that acleavage had been formed at the contacting part of the pattern with thesubstrate, which is the so-called undercut. However, generation of theabove-mentioned undercut can be prevented by formulating an aminecompound having a carboxyl group but not having a hydrogen atomcovalently bonded to a nitrogen atom of a basic center.

In the point of preventing from generation of the above-mentionedundercut, a tertiary amine not having a hydrogen atom covalently bondedto a nitrogen atom of a basic center is preferred than the aminecompound having a hydrogen atom covalently bonded to a nitrogen atom ofa basic center such as a primary amine having a carboxyl group since theformer shows the effect to its maximum.

Also, among the above-mentioned tertiary amines, if it is a compoundshowing stronger basicity than the amine compound of a weak base inwhich a nitrogen contained in the aromatic ring is a basic center suchas 2-quinolinecarboxylic acid and nicotinic acid, the carboxyl groupsare well arranged at the substrate side, and inactivation of thegenerated acid derived from the acid generator, etc., by diffusing tothe substrate can be more effectively prevented.

The problem of the undercut is likely caused in the case of thesubstrate where the material at the surface comprises a nitridedcompound such as TiN, SiN, SiON, etc., in particular, it is extremelyeasily caused in either of the case where the surface is a metal chromiccompound, or where it is metal chromium or a chromium compoundcontaining nitrogen and/or oxygen, and it is difficult to solve theproblem. However, when the resist composition of the present inventioncontaining the above-mentioned basic compound is used, a pattern havinggood profile can be formed even onto the substrate the outermost surfaceof which is a chromic compound, and the composition can beadvantageously used in the processing of a photomask blank, etc.

Specific examples of the chemical structures of the above-mentionedamine compound having a carboxyl group but not having a hydrogen atomcovalently bonded to a nitrogen atom of a basic center may be preferablymentioned a basic compound including the amine compound and theamineoxide compound represented by the following general formulae (7) to(9), but the invention is not limited by these,

wherein each R¹² and R¹³ represent a linear, branched or cyclic alkylgroup having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbonatoms, an aralkyl group having 7 to 20 carbon atoms, a hydroxyalkylgroup having 2 to 20 carbon atoms, an alkoxyalkyl group having 2 to 20carbon atoms, an acyloxyalkyl group having 2 to 20 carbon atoms, or analkylthioalkyl group having 2 to 20 carbon atoms, or R¹² and R¹³ may bebonded to form a cyclic structure with the nitrogen atom to which theyare bonded; R¹⁴ represents a hydrogen atom, a linear, branched or cyclicalkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20carbon atoms, an aralkyl group having 7 to 20 carbon atoms, ahydroxyalkyl group having 2 to 20 carbon atoms, an alkoxyalkyl grouphaving 2 to 20 carbon atoms, an acyloxyalkyl group having 2 to 20 carbonatoms, an alkylthioalkyl group having 2 to 20 carbon atoms, or a halogenatom; R¹⁵ represents a single bond, a linear, branched or cyclicalkylene group having 1 to 20 carbon atoms, or an arylene group having 6to 20 carbon atoms; R¹⁶ represents a linear or branched alkylene grouphaving 2 to 20 carbon atoms which may be substituted, and the alkylenegroup may contain one or a plural number of a carbonyl group(s) (—CO—),an ether group(s) (—O—), an ester group(s) (—COO—), a sulfide bond(s)(—S—) between carbon-carbon bond of the alkylene group; and R¹⁷represents a linear, branched or cyclic alkylene group having 1 to 20carbon atoms, or an arylene group having 6 to 20 carbon atoms.

In the above-mentioned general formulae (7) to (9), the linear, branchedor cyclic alkyl group having 1 to 20 carbon atoms may be specificallyexemplified by a methyl group, an ethyl group, a propyl group, anisopropyl group, a butyl group, an isobutyl group, a t-butyl group, apentyl group, a hexyl group, a decyl group, a cyclopentyl group, acyclohexyl group and a decahydronaphthalenyl group, the aryl grouphaving 6 to 20 carbon atoms may be specifically exemplified by a phenylgroup, a naphthyl group, an anthryl group, a phenanthryl group, apyrenyl group, a naphthacenyl group and a fluorenyl group, the aralkylgroup having 7 to 20 carbon atoms may be specifically exemplified by abenzyl group, a phenethyl group, a phenylpropyl group, a naphthylmethylgroup, a naphthylethyl group and an anthracenylmethyl group, thehydroxyalkyl group having 2 to 20 carbon atoms, preferably 2 to 10carbon atoms may be specifically exemplified by a hydroxymethyl group, ahydroxyethyl group and a hydroxypropyl group, the alkoxyalkyl grouphaving 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms may bespecifically exemplified by a methoxymethyl group, an ethoxymethylgroup, a propoxymethyl group, an isopropoxymethyl group, a butoxymethylgroup, an isobutoxymethyl group, a t-butoxymethyl group, at-amyloxymethyl group, a cyclohexyloxymethyl group and acyclopentyloxymethyl group, the acyloxyalkyl group having 2 to 20 carbonatoms, preferably 2 to 10 carbon atoms may be specifically exemplifiedby a formyloxymethyl group, an acetoxymethyl group, a propionyloxymethylgroup, a butyryloxymethyl group, a pivaloyloxymethyl group, acyclohexanecarbonyloxymethyl group and a decanoyloxymethyl group, thealkylthioalkyl group having 2 to 20 carbon atoms, preferably 2 to 10carbon atoms may be specifically exemplified by a methylthiomethylgroup, an ethylthiomethyl group, a propylthiomethyl group, anisopropylthiomethyl group, a butylthiomethyl group, anisobutylthiomethyl group, a t-butylthiomethyl group, a t-amylthiomethylgroup, a decylthiomethyl group and a cyclohexylthiomethyl group,respectively, but the invention is not limited by these.

Preferred specific examples of the amine compound represented by thegeneral formula (7) are exemplified in the following, but the inventionis not limited by these.

o-dimethylaminobenzoic acid, p-dimethylaminobenzoic acid,m-dimethylaminobenzoic acid, p-diethylaminobenzoic acid,p-dipropylaminobenzoic acid, p-diisopropylaminobenzoic acid,p-dibutylaminobenzoic acid, p-dipentylaminobenzoic acid,p-dihexylaminobenzoic acid, p-diethanolaminobenzoic acid,p-diisopropanolaminobenzoic acid, p-dimethanolaminobenzoic acid,2-methyl-4-diethylaminobenzoic acid, 2-methoxy-4-diethylaminobenzoicacid, 3-dimethylamino-2-naphthalene acid, 3-diethylamino-2-naphthaleneacid, 2-dimethylamino-5-bromobenzoic acid,2-dimethylamino-5-chlorobenzoic acid, 2-dimethylamino-5-iodobenzoicacid, 2-dimethylamino-5-hydroxybenzoic acid,4-dimethylamino-phenylacetic acid, 4-dimethylaminophenylpropionic acid,4-dimethylaminophenylbutyric acid, 4-dimethylaminophenylmalic acid,4-dimethylaminophenylpyruvic acid, 4-dimethylamino-phenyllactic acid,2-(4-dimethylaminophenyl)benzoic acid,2-(4-(dibutylamino)-2-hydroxybenzoyl)benzoic acid.

Preferred specific examples of the amineoxide compound represented bythe general formula (8) may be mentioned those in which the aminecompounds specifically exemplified by the above-mentioned generalformula (7) are oxidized, but the invention is not limited by these.

Preferred specific examples of the amine compound represented by thegeneral formula (9) are exemplified in the following, but the inventionis not limited by these.

1-piperidinepropionic acid, 1-piperidinebutyric acid, 1-piperidinemalicacid, 1-piperidinepyruvic acid, 1-piperidinelactic acid

The chemically amplified negative resist composition of the presentinvention may contain the above-mentioned basic compound of the aminecompound, the amineoxide compound, etc., as one kind or two or morekinds in combination.

To the chemically amplified negative resist composition of the presentinvention may be added an organic solvent for improving coating propertyto the workpiece, etc. Specific examples of the organic solvent may beexemplified by those disclosed at the paragraph[0144] of Japanese PatentLaid-Open Publication No. 2008-111103.

A formulation amount of the organic solvent is preferably 200 to 3,000parts by mass based on 100 parts by mass of the base resin, andparticularly 400 to 2,500 parts by mass are suitable.

To the chemically amplified negative resist composition of the presentinvention may be added a surfactant commonly used for improving coatingproperty. When the surfactant is used, a lot of surfactants have beenconventionally known as many examples are disclosed in InternationalPatent Laid-Open Publication No. 2006/121096, Japanese Patent Laid-OpenPublication No. 2008-102383, Japanese Patent Laid-Open Publication No.2008-304590, Japanese Patent Laid-Open Publication No. 2004-115630 andJapanese Patent Laid-Open Publication No. 2005-8766, and a suitablesurfactant can be selected by referring to these.

An amount of the surfactant to be added is preferably 2 parts by mass orless, more preferably 1 part by mass or less and 0.01 part by mass ormore based on 100 parts by mass of the base polymer in the chemicallyamplified resist composition.

Also, the chemically amplified negative resist composition of thepresent invention may further contain other kinds of onium salt(s) inaddition to the above-mentioned onium salt.

When such a chemically amplified negative resist composition isemployed, acid diffusion at the time of exposure can be effectivelycontrolled by the action of the onium salt contained therein, undercutof the pattern can be effectively suppressed by containing the basiccompound and it has adhesion to the workpiece and good etchingselectivity to the workpiece so that a pattern which is fine and havinghigh resolution, and reduced in LER can be obtained.

[Patterning Process]

The present invention further provides a patterning process whichcomprises the steps of forming a resist film on a workpiece using theabove-mentioned chemically amplified negative resist composition,irradiating a high energy beam to the resist film, and developing theresist film after irradiation using an alkaline developer to obtain aresist pattern.

In the patterning process of the present invention, a pattern can beformed by employing the conventionally known lithography technology.Generally, the above-mentioned chemically amplified negative resistcomposition is coated on a workpiece exemplified by a substrate (Si,SiO₂, SiN, SiON, TiN, WSi, BPSG, SOG, an organic anti-reflecting film,etc.) for manufacturing an integrated circuit or a substrate (Cr, CrO,CrON, MoSi, etc.) for manufacturing a mask circuit, etc., by the meansof spin coating, etc., so as to make a film thickness of 0.03 to 2.0 μm,and the film is prebaked on a hot plate at 60 to 150° C. for 1 to 20minutes, preferably at 80 to 140° C. for 1 to 10 minutes to form aresist film.

Then, by using a mask for forming an objective pattern, or directly bybeam exposure, a high-energy beam such as ultraviolet beam, farultraviolet beam, an electron beam, EUV, X ray, γ beam, synchrotronradiation ray, etc., is pattern irradiated with an exposure dose of, forexample, 1 to 200 mJ/cm², preferably 10 to 100 mJ/cm². Incidentally, thechemically amplified negative resist composition of the presentinvention is particularly effective in the case of pattern irradiationusing EUV or an electron beam. Exposure may be carried out by the usualexposure method as well as, in some cases, the immersion method in whichimmersion is carried out between the mask and the resist. In such acase, it is possible to use a top coat insoluble in water.

Next, the film is subjected to post-exposure bake (PEB) on a hot plateat 60 to 150° C. for 1 to 20 minutes, preferably at 80 to 140° C. for 1to 10 minutes. Further, by using a developer of an aqueous alkalisolution containing 0.1 to 5% by mass, preferably 2 to 3% by mass oftetramethylammonium hydroxide (TMAH), etc., development is carried outby the conventional method such as a dipping method, a puddle method, aspray method, etc., for example, for 0.1 to 3 minutes, preferably for0.5 to 2 minutes, to dissolve the unexposed area not formingcross-linked structure in the resist film and form an objective(negative) pattern on the substrate.

Incidentally, the resist composition of the present invention hasparticularly high etching resistance so that it can endure severeetching conditions, and it is useful when it is used under theconditions that require little line edge roughness. Also, it isparticularly useful, as a substrate to be processed, for a substratehaving a material which likely causes pattern peeling-off or patternfall on the surface thereof by the reason that adhesion of the resistpattern is poor, and is useful for forming a pattern on a substrate onwhich a film is formed by sputtering metal chromium or a chromiumcompound containing one or more light elements such as oxygen, nitrogenand carbon at the outermost surface as a layer, in particular, on aphotomask blank.

Such a patterning process is employed, by using the above-mentionedchemically amplified negative resist composition for forming a resistfilm, acid diffusion at the time of exposure can be effectivelycontrolled, and even when a substrate (in particular, a photomask blank)having a layer containing chromium at the outermost surface is used as aworkpiece, an effect of a generating acid such as undercut, etc., can besuppressed, so that a pattern having high resolution and reduced in LERcan be formed. In addition, adhesion between the resist film and theworkpiece as well as etching selectivity are good, and occurrence ofpattern fall or poor pattern transferring, etc. can be suppressed when afine pattern is formed thinning of the resist film, so that it can besuitably used for microprocessing technology, in particular, for anelectron beam and EUV lithography technology.

EXAMPLES

In the following, the present invention is specifically explained byreferring to Synthesis Examples, Examples and Comparative Example, butthe present invention is not limited by the following Examples.Incidentally, in the following examples, Me represents a methyl group.Also, the copolymerization composition ratio is a molar ratio, and theweight average molecular weight (Mw) shows a weight average molecularweight in terms of a polystyrene by gel permeation chromatography (GPC).

Synthesis Example 1 Synthesis of Onium Salt

The onium salt contained in the chemically amplified negative resistcomposition of the present invention was synthesized by the schemementioned below. The structures of the synthesized onium salts (Q-1 toQ-4) to be used in the present invention and the structures of the oniumsalts (Comparative Q-1 to Q-4) to be used in Comparative Examples wereshown in Table 5 mentioned later.

Synthesis Example 1-1 Synthesis of Q-1 Synthesis Example 1-1-1 Synthesisof 2-trifluoromethylbicyclo[2,2,2,1]hepta-5-ene-2-carboxylic acid (20)

22.7 g of cyclopentadiene (18) and 40.0 g of trifluoromethylacrylic acid(19) were stirred at room temperature in 40 g of benzene overnight. 20 gof hexane was poured into the reaction mixture to precipitate whitesolid and the precipitate was collected by filtration to obtain 45.6 g(Yield: 77%) of the carboxylic acid (20).

Synthesis Example 1-1-2 Synthesis of sodium2-trifluoromethylbicyclo[2,2,1]hepta-5-ene-2-carboxylate (21)

5.0 g of the carboxylic acid (20) obtained in (Synthesis Example 1-1-1)was dissolved in 10.0 g of methylene chloride, and 2.0 g of sodiumhydrogen carbonate and 10 g of water were added to the solution and theresulting mixture was stirred overnight. Methylene chloride and waterwere distilled off under reduced pressure to obtain sodium carboxylate(21). This material was used in the next reaction without purificationany more.

Synthesis Example 1-1-3 Synthesis of triphenylsulfonium2-trifluoromethylbicyclo[2,2,1]hepta-5-ene-2-carboxylate (Q-1)

Sodium carboxylate (21) obtained in (Synthesis Example 1-1-2) wasdissolved in 20 g of methylene chloride, 40 g of an aqueous solution oftriphenylsulfonium chloride (22) was added to the solution and theresulting mixture was stirred for 30 minutes. The organic layer wasseparated, the aqueous layer was extracted with CH₂Cl₂, and the combinedorganic layers were washed three times with H₂O. The solvent wasdistilled off under reduced pressure to obtain 4.6 g of the objectivematerial, onium salt (Q-1) (Yield: 40%).

Synthesis Example 1-2 Synthesis of Q-2

Synthesis was carried out in the same manner except for changingcyclopentadiene in the synthesis of Q-1 in Synthesis Example 1-1 tofuran to obtain 3.8 g (three-step yield: 29%) of Q-2.

Synthesis Example 1-3 Synthesis of Q-3

2-Trifluoromethylbicyclo[2,2,1]hepta-5-ene-2-carboxylic acid (20)obtained in Synthesis Example 1-1-1 was stirred in a toluene solvent inthe presence of 5% Pd/C catalyst at room temperature under hydrogenatmosphere to obtain 2-trifluoromethylbicyclo[2,2,1]heptane-2-carboxylicacid. In the same synthetic routes as in Synthesis Example 1-1-2 to1-1-3 except for using the carboxylic acid as the starting material toobtain 3.9 g (four-step yield: 32%) of Q-3.

Synthesis Example 1-4 Synthesis of Q-4

In the same synthetic routes as in Synthesis Example 1-1-2 to 1-1-3except for changing the carboxylic acid (20) in Synthesis Example(1-1-2) to the carboxylic acid represented by the following formula (23)to obtain 2.8 g (two-step yield: 33%) of Q-4.

Synthesis Example 2 Synthesis of Base Resin

The base resins (polymers) used in the resist compositions of thepresent invention were synthesized by the following scheme. Thecomposition ratios of the synthesized respective polymers were shown inTable 1, and the structures of the repeating units were shown in Table 2to Table 4.

Polymer Synthesis Example 2-1 Synthesis of Polymer 1

To 3 L of a flask were added 238.0 g of acetoxystyrene, 22.6 g of4-chlorostyrene and 189.4 g of indene, and 675 g of toluene as asolvent. The reaction apparatus was cooled to −70° C. under nitrogenatmosphere, and degassing under reduced pressure and nitrogen flow wererepeated three times. After the temperature was raised to roomtemperature, 40.5 g of 2,2′-azobis(2,4-dimethylvaleronitrile) (V-65available from Wako Pure Chemical Industries, Ltd.) was added to themixture as a polymerization initiator, and after the temperature wasraised to 45° C., the reaction was carried out for 20 hours, then, thetemperature was raised to 55° C., the reaction was further carried outfor 20 hours. The reaction solution was concentrated to a half volume,the concentrate was precipitated in 15.0 L of a methanol solution, andthe obtained white solid was collected by filtration and dried at 40° C.under reduced pressure to obtain 311 g of a white polymer.

The polymer was dissolved again in 488 g of methanol and 540 g oftetrahydrofuran, and 162 g of triethylamine and 32 g of water were addedto the solution to carry out the deprotection reaction at 60° C. for 40hours. The reaction mixture was concentrated as a fractionating step,then, the concentrate was dissolved in a mixed solvent comprising 548 gof methanol and 112 g of acetone, and to the dissolved solution wasadded dropwise 990 g of hexane over 10 minutes. The mixed white turbidliquid was allowed to stand to separate the liquids, and the lower layer(polymer layer) was taken out and concentrated. The polymer concentratedagain was further dissolved in a mixed solvent comprising 548 g ofmethanol and 112 g of acetone, the dissolved solution was subjected todispersing and liquid separating operations using 990 g of hexane, andthe obtained lower layer (polymer layer) was concentrated. Theconcentrated liquid was dissolved in 870 g of ethyl acetate, and thesolution was subjected to neutralization, liquid separation and washingwith a mixed solution comprising 250 g of water and 98 g of acetic acidonce, and further with 225 g of water and 75 g of pyridine once, andliquid separation and washing with 225 g of water four times.Thereafter, the ethyl acetate solution of the upper layer wasconcentrated, the concentrate was dissolved in 250 g of acetone,precipitated in 15 L of water, and the precipitate was collected byfiltration and vacuum dried at 50° C. for 40 hours to obtain 187 g of awhite polymer. This is made (Polymer 1).

The obtained polymer (Polymer 1) was measured by ¹³C, ¹H-NMR and GPC,and the following analytical results were obtained.

-   Copolymerization composition ratio (Molar ratio)-   Hydroxystyrene:4-chlorostyrene:indene=78.0:11.0:11.0-   Weight average molecular weight (Mw)=4500-   Molecular weight distribution (Mw/Mn)=1.65

Polymer Synthesis Example 2-2 Synthesis of Polymer 2

Under a nitrogen atmosphere, into 3 L of a cylinder for dropping werecharged 380.0 g of 4-acetoxystyrene, 70.0 g of 4-chlorostyrene, 50.1 gof acenaphthylene and 59 g of dimethyl-2,2′-azobis-(2-methylpropionate)(V-601 available from Wako Pure Chemical Industries, Ltd.), and 900 g oftoluene was added thereto as a solvent to prepare a solution. Into 3 Lof a separate flask for polymerization which had been made under anitrogen atmosphere was charged 300.0 g of toluene, and under thecondition that the solvent was heated to 80° C., the solution preparedas mentioned above was added dropwise thereinto over 4 hours. Aftercompletion of the dropwise addition, stirring was continued for 18 hourswhile maintaining the polymerization temperature to 80° C., and then,the mixture was cooled to room temperature. The obtained polymerizationliquid was added dropwise to 10 kg of a hexane, and the precipitatedcopolymer was collected by filtration. The separated copolymer byfiltration was washed twice with 2,000 g of a mixed solution ofhexane:toluene=10:1. The obtained copolymer was dissolved in 3 L of aflask under nitrogen atmosphere in a mixed solvent comprising 1,260 g oftetrahydrofuran and 420 g of methanol, and 180 g of ethanolamine wasadded thereto and the resulting mixture was stirred at 60° C. for 3hours. The reaction mixture was concentrated under reduced pressure, theresulting concentrate was dissolved in a mixed solvent comprising 3,000g of ethyl acetate and 800 g of water, the obtained solution wastransferred into a separating funnel, and 90 g of acetic acid was addedthereto to carry out liquid separating operation. The lower layer wasremoved, and the obtained organic layer was added 800 g of water and 121g of pyridine to carry out liquid separating operation. The lower layerwas removed, and the obtained organic layer was further added 800 g ofwater to carry out washing and liquid separating operation (washing andliquid separating operation was five times in total). At the time ofallowing to stand at each liquid separating step, when 150 g of acetonewas added and the mixture was gently stirred, then, liquid separationwas well carried out with good separation.

The organic layer after liquid separation was concentrated, theconcentrate was dissolved in 1,200 g of acetone, and the acetonesolution passed through 0.02 μm of a Nylon filter was added dropwise to10 L of water. The obtained crystallized precipitate was collected byfiltration and washed with water, and subjected to suction filtrationfor 2 hours. The mass collected by filtration was dissolved in 1,200 gof acetone again, and the acetone solution passed through 0.02 μm of aNylon filter was added dropwise to 10 kg of water. The obtainedcrystallized precipitate was collected by filtration and washed withwater, and dried to obtain 400 g of a white polymer. This is made(Polymer 2).

The obtained polymer (Polymer 2) was measured by ¹³C-NMR and GPC, andthe following analytical results were obtained.

-   Copolymerization composition ratio (Molar ratio)-   Hydroxystyrene:4-chlorostyrene:acenaphthylene=75.0:15.0:10.0-   Weight average molecular weight (Mw)=4100-   Molecular weight distribution (Mw/Mn)=1.72

Polymer Synthesis Example 2-3 to 2-10 Syntheses of Polymers 3 to 10

The resins shown in Table 1 were manufactured according to theprocedures used in Polymer Synthesis Examples 1 and 2 as a basis exceptfor changing the kind and the formulation ratio of the respectivemonomers.

The structures of each unit in Table 1 are shown in Tables 2 to 4.Incidentally, in the following Table 1, the introducing ratio shows amolar ratio.

TABLE 1 Intro- Intro- Intro- ducing ducing ducing ratio ratio ratio Unit1 (mole %) Unit 2 (mole %) Unit 3 (mole %) Polymer A-1 75.0 B-1 15.0 C-110.0 1 Polymer A-1 75.0 B-1 15.0 C-2 10.0 2 Polymer A-1 79.0 B-3 15.0C-1 10.0 3 Polymer A-1 67.0 B-4 15.0 C-1 10.0 4 Polymer A-1 78.0 B-111.0 C-2 11.0 5 Polymer A-1 78.0 B-2 11.0 C-2 11.0 6 Polymer A-2 68.0B-1 22.0 C-1 10.0 7 Polymer A-2 68.0 B-3 22.0 C-1 10.0 8 Polymer A-266.0 B-1 20.0 C-3 14.0 9 Polymer A-2 66.0 B-3 20.0 C-3 14.0 10

TABLE 2

A-1

A-2

TABLE 3

B-1

B-2

B-3

B-4

TABLE 4

C-1

C-2

C-3Preparation of Negative Resist Composition

The onium salts (Q-1 to Q-4) synthesized as mentioned above, the oniumsalts for comparative purpose (Comparative Q-1 to Comparative Q-4), thepolymers (Polymer 1 to Polymer 10), photoacid generators, basiccompounds and crosslinking agents the structures of which were shownbelow were dissolved in organic solvents with the compositions shown inTable 6 to prepare respective resist compositions, and further therespective compositions were filtered through a 0.2 μm size filter or a0.02 μm size Nylon or UPE filter to prepare solutions of negative resistcompositions, respectively. The acid generators used have the structuresshown by the following PAG-1 and PAG-2, and the basic component used isthe compound of the following Base-1. Also, the structures of the usedonium salts are shown in the following Table 5.

TABLE 5

Q-1

Q-2

Q-3

Q-4 Comparative Q-1

Comparative Q-2

Comparative Q-3

Comparative Q-4

The organic solvents in Table 6 are PGMEA (propylene glycol monomethylether acetate), EL (ethyl lactate), PGME (propylene glycol monomethylether) and CyH (cyclohexanone). Also, the crosslinking agent istetramethoxymethyl glycol urea (TMGU). Further, to the compositions ofthe respective examples was each added 0.075 part by mass of PF-636(available from OMNOVA SOLUTIONS, Inc.) as a surfactant other than thosedescribed in Table 6.

TABLE 6 Acid Cross- diffusion Photoacid linking Solvent Solvent Solventcontroller Resin generator agent 1 2 3 Example 1 Q-1 (3.6) Polymer PAG-1(8) TMGU PGMEA EL — 1 (80) PAG-2 (2) (8.2) (640) (2,170) Example 2 Q-1(3.0) Polymer PAG-1 (8) TMGU PGMEA EL — Comparative 1 (80) PAG-2 (2)(8.2) (640) (2,170) Q-1 (0.3) Example 3 Q-1 (3.0) Polymer PAG-1 (8) TMGUPGMEA EL — Base-1 (0.3) 1 (80) PAG-2 (2) (8.2) (640) (2,170) Example 4Q-1 (3.0) Polymer PAG-1 (8) TMGU PGMEA EL — Comparative 1 (80) PAG-2 (2)(8.2) (640) (2,170) Q-1 (0.15) Base-1 (0.15) Example 5 Q-1 (3.6) PolymerPAG-1 (8) TMGU PGMEA EL — 2 (80) PAG-2 (2) (8.2) (640) (2,170) Example 6Q-1 (3.6) Polymer PAG-1 (8) TMGU PGMEA EL — 3 (80) PAG-2 (2) (8.2) (640)(2,170) Example 7 Q-1 (3.6) Polymer PAG-1 (8) TMGU PGMEA EL — 4 (80)PAG-2 (2) (8.2) (640) (2,170) Example 8 Q-1 (3.6) Polymer PAG-1 (8) TMGUPGMEA EL — 5 (80) PAG-2 (2) (8.2) (640) (2,170) Example 9 Q-1 (3.0)Polymer PAG-1 (8) TMGU PGMEA EL — Base-1 (0.3) 5 (80) PAG-2 (2) (8.2)(640) (2,170) Example 10 Q-1 (3.6) Polymer PAG-1 (8) TMGU PGMEA EL — 6(80) PAG-2 (2) (8.2) (640) (2,170) Example 11 Q-1 (3.6) Polymer PAG-1(8) TMGU PGMEA EL — 7 (80) PAG-2 (2) (8.2) (640) (2,170) Example 12 Q-1(3.6) Polymer PAG-1 (8) TMGU PGMEA EL — 8 (80) PAG-2 (2) (8.2) (640)(2,170) Example 13 Q-2 (3.6) Polymer PAG-1 (8) TMGU PGMEA EL — 1 (80)PAG-2 (2) (8.2) (640) (2,170) Example 14 Q-2 (3.0) Polymer PAG-1 (8)TMGU PGMEA EL — Base-1 (0.3) 1 (80) PAG-2 (2) (8.2) (640) (2,170)Example 15 Q-2 (3.6) Polymer PAG-1 (8) TMGU PGMEA EL — 5 (80) PAG-2 (2)(8.2) (640) (2,170) Example 16 Q-2 (3.0) Polymer PAG-1 (8) TMGU PGMEA EL— Base-1 (0.3) 5 (80) PAG-2 (2) (8.2) (640) (2,170) Example 17 Q-3 (3.6)Polymer PAG-1 (8) TMGU PGMEA EL — 1 (80) PAG-2 (2) (8.2) (640) (2,170)Example 18 Q-3 (3.0) Polymer PAG-1 (8) TMGU PGMEA EL — Base-1 (0.3) 1(80) PAG-2 (2) (8.2) (640) (2,170) Example 19 Q-3 (3.6) Polymer PAG-1(8) TMGU PGMEA EL — 5 (80) PAG-2 (2) (8.2) (640) (2,170) Example 20 Q-3(3.0) Polymer PAG-1 (8) TMGU PGMEA EL — Base-1 (0.3) 5 (80) PAG-2 (2)(8.2) (640) (2,170) Example 21 Q-4 (3.6) Polymer PAG-1 (8) TMGU PGMEA EL— 1 (80) PAG-2 (2) (8.2) (640) (2,170) Example 22 Q-4 (3.0) PolymerPAG-1 (8) TMGU PGMEA EL — Base-1 (0.3) 1 (80) PAG-2 (2) (8.2) (640)(2,170) Example 23 Q-4 (3.6) Polymer PAG-1 (8) TMGU PGMEA EL — 5 (80)PAG-2 (2) (8.2) (640) (2,170) Example 24 Q-4 (3.0) Polymer PAG-1 (8)TMGU PGMEA EL — Base-1 (0.3) 5 (80) PAG-2 (2) (8.2) (640) (2,170)Example 25 Q-1 (3.6) Polymer PAG-1 (8) TMGU PGMEA CyH PGME 9 (80) (8.2)(800) (1,600) (400) Example 26 Q-1 (3.6) Polymer PAG-1 (8) TMGU PGMEACyH PGME 10 (80) (8.2) (800) (1,600) (400) Comparative ComparativePolymer PAG-1 (8) TMGU PGMEA EL — Example 1 Q-1 (1.7) 1 (80) PAG-2 (2)(8.2) (640) (2,170) Comparative Comparative Polymer PAG-1 (8) TMGU PGMEAEL — Example 2 Q-1 (1.4) 1 (80) PAG-2 (2) (8.2) (640) (2,170) Base-1(0.3) Comparative Comparative Polymer PAG-1 (8) TMGU PGMEA EL — Example3 Q-2 (2.4) 1 (80) PAG-2 (2) (8.2) (640) (2,170) Comparative ComparativePolymer PAG-1 (8) TMGU PGMEA EL — Example 4 Q-3 (2.4) 1 (80) PAG-2 (2)(8.2) (640) (2,170) Comparative Comparative Polymer PAG-1 (8) TMGU PGMEAEL — Example 5 Q-4 (2.5) 1 (81) PAG-2 (3) (8.3) (641) (2,171)Comparative Comparative Polymer PAG-1 (8) TMGU PGMEA CyH PGME Example 6Q-1 (1.7) 9 (80) (8.2) (800) (1,600) (400) Comparative ComparativePolymer PAG-1 (8) TMGU PGMEA CyH PGME Example 7 Q-2 (2.4) 9 (80) (8.2)(800) (1,600) (400)

Evaluation of Electron Beam Drawing Examples 1 to 24 and ComparativeExamples 1 to 5

Each of the negative resist composition (Examples 1 to 24 andComparative Examples 1 to 5) prepared as mentioned above was spin coatedonto a 152-mm square mask blank having a chromium oxynitride film at theoutermost surface using ACT-M (manufactured by Tokyo Electron Limited),and pre-baked on a hot plate at 110° C. for 600 seconds to form a resistfilm with a film thickness of 90 nm. The film thickness of the obtainedresist film was measured by using an optical film thickness measurementsystem Nanospec (manufactured by Nanometrics Inc.). Measurement was madeat 81 points on surface of the blank substrate excluding an outer edgepart within 10 mm inward from the blank periphery, and an average filmthickness and a film thickness range were calculated therefrom.

Further, the coated mask blanks were exposed to an electron beamexposure apparatus (EBM-5000 plus, accelerating voltage: 50 keV,manufactured by NuFlare Technology Inc.), then, baked at 90° C. for 600seconds (PEB: post exposure bake), and developed with a 2.38% by mass oftetramethylammonium hydroxide aqueous solution, whereby negativepatterns could be obtained. Further, the obtained resist patterns wereevaluated as follows.

The prepared patterned mask blank was observed under a top-down scanningelectron microscope (SEM), the exposure dose which provided a 400 nmresolution at a 400 nm 1:1 line and space (LS) pattern and 1:50 isolatedspace pattern was defined to be the optimum exposure dose (μC/cm²), theminimum dimension at the exposure dose was defined to be the resolution(limiting resolution), and with regard to edge roughness, the exposuredose which provided a 1:1 resolution at the top and bottom of a 400 nm1:1 line and space pattern was defined to be the optimum exposure dose(μC/cm²) and the edge roughness with 400 nm LS was measured by SEM. Withregard to the pattern profile, it was judged whether it is rectangularor not with naked eyes. In addition, CD uniformity (CDU) was evaluatedat 49 points on surface of the blank substrate excluding an outer edgepart within 20 mm inward from the blank periphery, by measuring the linewidth at the exposure dose (pC/cm²) which provided a 1:1 resolution atthe top and bottom of a 400 nm 1:1 line and space pattern, and 30 valueof the value in which each measured point was deducted from the averagevalue of the line width was calculated. Evaluation results of the resistcompositions of the present invention and the resist compositions forcomparison in the electron beam drawing are shown in the following Table7.

TABLE 7 Optimum Exposure Limiting Limiting Dose (LS) ResolutionResolution CDU (3σ) Pattern (μC/cm²) (LS) (nm) (IS) (nm) LER (nm) (nm)Profile Example 1 34 40 40 4.6 2.3 Rectangular Example 2 35 40 40 4.82.2 Rectangular Example 3 34 40 40 4.7 2.1 Rectangular Example 4 29 4040 4.7 2.4 Rectangular Example 5 31 40 40 4.8 2.5 Rectangular Example 632 40 40 4.8 2.4 Rectangular Example 7 34 40 40 4.5 2.2 RectangularExample 8 35 40 40 4.5 2.5 Rectangular Example 9 32 40 40 4.5 2.4Rectangular Example 10 33 40 40 4.9 2.3 Rectangular Example 11 31 40 404.8 2.2 Rectangular Example 12 33 40 40 4.9 2.3 Rectangular Example 1333 40 40 4.9 2.4 Rectangular Example 14 34 40 40 4.8 2.2 RectangularExample 15 34 40 40 4.8 2.3 Rectangular Example 16 33 40 40 4.8 2.3Rectangular Example 17 33 40 40 4.8 2.4 Rectangular Example 18 34 40 404.6 2.3 Rectangular Example 19 34 40 40 4.7 2.4 Rectangular Example 2035 40 40 4.9 2.4 Rectangular Example 21 35 40 40 4.6 2.5 RectangularExample 22 35 40 40 4.5 2.3 Rectangular Example 23 35 40 40 4.8 2.4Rectangular Example 24 35 40 40 4.8 2.4 Rectangular Comparative 34 50 556.5 3.6 Rectangular Example 1 Comparative 34 50 55 6.2 3.5 RectangularExample 2 Comparative 34 50 55 5.6 3.6 Rectangular Example 3 Comparative34 50 55 5.6 3.6 Rectangular Example 4 Comparative 12 55 55 7.3 3.8Rectangular Example 5

Evaluation of EUV Exposure Examples 25 and 26 and Comparative Examples 6and 7

The negative resist compositions (Examples 25 and 26 and ComparativeExamples 6 and 7) prepared as mentioned above were each spin coated onan Si substrate having a diameter of 4 inches which had been subjectedto the hexamethyldisilazane (HMDS) vapor prime treatment, and pre-bakedon a hot plate at 105° C. for 60 seconds to form a resist film with athickness of 50 nm. This was subjected to EUV exposure with NA0.3 anddipole illumination.

The coated substrate was subjected to post-exposure bake (PEB) for 60seconds on a hot plate immediately after exposure and to paddledevelopment with 2.38% by mass of TMAH aqueous solution for 80 seconds,whereby the positive pattern was obtained.

The obtained resist pattern was evaluated as follows. The minimumdimension at the exposure dose which provided a 1:1 resolution of a 100nm LS pattern was defined to be the resolution (limiting resolution),and the edge roughness (LER) of 100 nm LS pattern was measured by SEM.With regard to the pattern profile, it was judged whether it isrectangular or not with naked eyes. Evaluation results of the resistcompositions of the present invention and the resist compositions forcomparison in the EUV drawing are shown in Table 8.

TABLE 8 Optimum Exposure Limiting Dose Resolution LER Pattern (mJ/cm²)(nm) (nm) Profile Example 25 24 28 4.0 Rectangular Example 26 23 30 4.3Rectangular Comparative 22 35 7.0 Rectangular Example 6 Comparative 2335 6.5 Rectangular Example 7

The results in the above-mentioned Tables 7 and 8 are explained. Thechemically amplified negative resist composition of the presentinvention (Examples 1 to 24, and Examples 25 and 26) each showed goodresolution and good pattern rectangularity, and also showed good valuesin line edge roughness. On the other hand, the resist compositions usingthe amine compound in place of the onium salt to be used in the presentinvention or the resist compositions using the onium salt having nofluorine atom at the α-position of the carboxyl group of ComparativeExamples 1 to 5 and Comparative Examples 6 and 7 showed bad results inresolution, line edge roughness and CDU as compared with those ofExamples. When the amine compound was used, the acid generated from thesulfonic acid could not cause the exchange reaction with the aminecompound, so that properties were considered to become worse. Also, theresist compositions using the onium salt having no fluorineatom-containing group at the α-position of the carboxyl group had alarge difference in a pKa from that of the sulfonic acid, so that thecause of deterioration of roughness was considered to be a rapidexchange reaction which did not occur. In addition, when the onium salthaving a pKa smaller than 1.5 was used in Comparative Example 5, theresist was highly sensitive, and the value of the line edge roughnessbecame large. This result can be considered that the pKa is high so thatit did not act as the acid diffusion controlling agent but act as theacid generator.

As can be clearly seen from the explanation mentioned above, when theresist composition of the present invention is employed, a pattern witha little line edge roughness can be formed by exposure. The patterningprocess using the same is useful for photolithography in semiconductormanufacturing, in particular, in the processing of photomask blanks.

It must be stated here that the present invention is not restricted tothe embodiments shown by the above-mentioned embodiments. Theabove-mentioned embodiments are merely examples so that any embodimentscomposed of substantially the same technical concept as disclosed in theclaims of the present invention and expressing a similar effect areincluded in the technical scope of the present invention.

What is claimed is:
 1. A chemically amplified negative resistcomposition which comprises an onium salt represented by the followinggeneral formula (0-1), a resin which becomes alkali insoluble by anaction of an acid and an acid generator,

wherein R^(f) represents a fluorine atom or a trifluoromethyl group; Yrepresents a cyclic hydrocarbon group having 3 to 30 carbon atoms, thehydrogen atom in the cyclic hydrocarbon group may be substituted by ahetero atom itself or a monovalent hydrocarbon group which may besubstituted by a hetero atom(s), and the hetero atom(s) may beinterposed into the cyclic structure of the cyclic hydrocarbon group andthe monovalent hydrocarbon group; and M⁺ represents a monovalent cation.2. The chemically amplified negative resist composition according toclaim 1, wherein the onium salt is represented by the following generalformula (1) or (2),

wherein R^(f) and M⁺ have the same meanings as defined above; Xrepresents O or CH₂; k¹ represents an integer of 0 to 2; and each Z¹,Z², Z³, Z⁴, Z⁵ and Z⁶ independently represent a hydrogen atom or alinear, branched or cyclic monovalent hydrocarbon group having 1 to 10carbon atoms which may be substituted by a hetero atom(s), and a heteroatom(s) may be interposed in the monovalent hydrocarbon group,

wherein R^(f), X, k¹, Z¹, Z², Z⁵, Z⁶ and M⁺ have the same meanings asdefined above.
 3. The chemically amplified negative resist compositionaccording to claim 1, wherein the resin contains a repeating unitrepresented by the following general formula (3) or a repeating unitrepresented by the following general formula (4), or both of them,

wherein each A and B represent a single bond or an alkylene group having1 to 10 carbon atoms which may contain an ether bond(s) in the chain ofthe alkylene group; each R¹ independently represents a hydrogen atom ora methyl group; each R^(X) independently represents a hydrogen atom oran alkyl group having 1 to 6 carbon atoms; X′ represents a hydrogenatom, a linear, branched or cyclic alkyl group having 1 to 20 carbonatoms, an alkoxyalkyl group having 2 to 20 carbon atoms, analkylthioalkyl group having 2 to 20 carbon atoms, a halogen atom, anitro group, a cyano group, a sulfinyl group or a sulfonyl group; Wrepresents an alkyl group having 1 to 20 carbon atoms or an acyl grouphaving 1 to 20 carbon atoms; “a” and “c” represent integers of 0 to 4;“b” represents an integer of 1 to 5; “d” represents an integer of 0 to5; each P and Q represent 0 or 1; and each “s” and “t” represent aninteger of 0 to
 2. 4. The chemically amplified negative resistcomposition according to claim 2, wherein the resin contains a repeatingunit represented by the following general formula (3) or a repeatingunit represented by the following general formula (4), or both of them,

wherein each A and B represent a single bond or an alkylene group having1 to 10 carbon atoms which may contain an ether bond(s) in the chain ofthe alkylene group; each R¹ independently represents a hydrogen atom ora methyl group; each R^(X) independently represents a hydrogen atom oran alkyl group having 1 to 6 carbon atoms; X′ represents a hydrogenatom, a linear, branched or cyclic alkyl group having 1 to 20 carbonatoms, an alkoxyalkyl group having 2 to 20 carbon atoms, analkylthioalkyl group having 2 to 20 carbon atoms, a halogen atom, anitro group, a cyano group, a sulfinyl group or a sulfonyl group; Wrepresents an alkyl group having 1 to 20 carbon atoms or an acyl grouphaving 1 to 20 carbon atoms; “a” and “c” represent integers of 0 to 4;“b” represents an integer of 1 to 5; “d” represents an integer of 0 to5; each P and Q represent 0 or 1; and each “s” and “t” represent aninteger of 0 to
 2. 5. The chemically amplified negative resistcomposition according to claim 1, wherein the resin contains a repeatingunit represented by the following general formula (5) or a repeatingunit represented by the following general formula (6), or both of them,

wherein “f” represents an integer of 0 to 6; each R³ independentlyrepresents a hydrogen atom, an alkyl group having 1 to 6 carbon atomswhich may be substituted by a halogen atom(s), a primary or secondaryalkoxy group which may be substituted by a halogen atom(s) or analkylcarbonyloxy group having 1 to 7 carbon atoms which may besubstituted by a halogen atom(s); “g” represents an integer of 0 to 4;each R⁴ independently represents a hydrogen atom, an alkyl group having1 to 6 carbon atoms which may be substituted by a halogen atom(s), aprimary or secondary alkoxy group which may be substituted by a halogenatom(s) or an alkylcarbonyloxy group having 1 to 7 carbon atoms whichmay be substituted by a halogen atom(s).
 6. The chemically amplifiednegative resist composition according to claim 2, wherein the resincontains a repeating unit represented by the following general formula(5) or a repeating unit represented by the following general formula(6), or both of them,

wherein “f” represents an integer of 0 to 6; each R³ independentlyrepresents a hydrogen atom, an alkyl group having 1 to 6 carbon atomswhich may be substituted by a halogen atom(s), a primary or secondaryalkoxy group which may be substituted by a halogen atom(s) or analkylcarbonyloxy group having 1 to 7 carbon atoms which may besubstituted by a halogen atom(s); “g” represents an integer of 0 to 4;each R⁴ independently represents a hydrogen atom, an alkyl group having1 to 6 carbon atoms which may be substituted by a halogen atom(s), aprimary or secondary alkoxy group which may be substituted by a halogenatom(s) or an alkylcarbonyloxy group having 1 to 7 carbon atoms whichmay be substituted by a halogen atom(s).
 7. The chemically amplifiednegative resist composition according to claim 3, wherein the resincontains a repeating unit represented by the following general formula(5) or a repeating unit represented by the following general formula(6), or both of them,

wherein “f” represents an integer of 0 to 6; each R³ independentlyrepresents a hydrogen atom, an alkyl group having 1 to 6 carbon atomswhich may be substituted by a halogen atom(s), a primary or secondaryalkoxy group which may be substituted by a halogen atom(s) or analkylcarbonyloxy group having 1 to 7 carbon atoms which may besubstituted by a halogen atom(s); “g” represents an integer of 0 to 4;each R⁴ independently represents a hydrogen atom, an alkyl group having1 to 6 carbon atoms which may be substituted by a halogen atom(s), aprimary or secondary alkoxy group which may be substituted by a halogenatom(s) or an alkylcarbonyloxy group having 1 to 7 carbon atoms whichmay be substituted by a halogen atom(s).
 8. The chemically amplifiednegative resist composition according to claim 4, wherein the resincontains a repeating unit represented by the following general formula(5) or a repeating unit represented by the following general formula(6), or both of them,

wherein “f” represents an integer of 0 to 6; each R³ independentlyrepresents a hydrogen atom, an alkyl group having 1 to 6 carbon atomswhich may be substituted by a halogen atom(s), a primary or secondaryalkoxy group which may be substituted by a halogen atom(s) or analkylcarbonyloxy group having 1 to 7 carbon atoms which may besubstituted by a halogen atom(s); “g” represents an integer of 0 to 4;each R⁴ independently represents a hydrogen atom, an alkyl group having1 to 6 carbon atoms which may be substituted by a halogen atom(s), aprimary or secondary alkoxy group which may be substituted by a halogenatom(s) or an alkylcarbonyloxy group having 1 to 7 carbon atoms whichmay be substituted by a halogen atom(s).
 9. The chemically amplifiednegative resist composition according to claim 1, wherein thecomposition further contains a crosslinking agent.
 10. The chemicallyamplified negative resist composition according to claim 2, wherein thecomposition further contains a crosslinking agent.
 11. The chemicallyamplified negative resist composition according to claim 3, wherein thecomposition further contains a crosslinking agent.
 12. The chemicallyamplified negative resist composition according to claim 4, wherein thecomposition further contains a crosslinking agent.
 13. The chemicallyamplified negative resist composition according to claim 1, wherein thecomposition further contains one or more basic compounds represented bythe following general formulae (7) to (9),

wherein each R¹² and R¹³ represent a linear, branched or cyclic alkylgroup having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbonatoms, an aralkyl group having 7 to 20 carbon atoms, a hydroxyalkylgroup having 2 to 20 carbon atoms, an alkoxyalkyl group having 2 to 20carbon atoms, an acyloxyalkyl group having 2 to 20 carbon atoms, or analkylthioalkyl group having 2 to 20 carbon atoms, or R¹² and R¹³ may bebonded to form a cyclic structure with the nitrogen atom to which theyare bonded; R¹⁴ represents a hydrogen atom, a linear, branched or cyclicalkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20carbon atoms, an aralkyl group having 7 to 20 carbon atoms, ahydroxyalkyl group having 2 to 20 carbon atoms, an alkoxyalkyl grouphaving 2 to 20 carbon atoms, an acyloxyalkyl group having 2 to 20 carbonatoms, an alkylthioalkyl group having 2 to 20 carbon atoms, or a halogenatom; R¹⁵ represents a single bond, a linear, branched or cyclicalkylene group having 1 to 20 carbon atoms, or an arylene group having 6to 20 carbon atoms; R¹⁶ represents a linear or branched alkylene grouphaving 2 to 20 carbon atoms which may be substituted, and the alkylenegroup may contain one or a plural number of a carbonyl group(s), anether group(s), an ester group(s) and a sulfide bond(s) betweencarbon-carbon bond of the alkylene group; and R¹⁷ represents a linear,branched or cyclic alkylene group having 1 to 20 carbon atoms, or anarylene group having 6 to 20 carbon atoms.
 14. The chemically amplifiednegative resist composition according to claim 2, wherein thecomposition further contains one or more basic compounds represented bythe following general formulae (7) to (9),

wherein each R¹² and R¹³ represent a linear, branched or cyclic alkylgroup having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbonatoms, an aralkyl group having 7 to 20 carbon atoms, a hydroxyalkylgroup having 2 to 20 carbon atoms, an alkoxyalkyl group having 2 to 20carbon atoms, an acyloxyalkyl group having 2 to 20 carbon atoms, or analkylthioalkyl group having 2 to 20 carbon atoms, or R¹² and R¹³ may bebonded to form a cyclic structure with the nitrogen atom to which theyare bonded; R¹⁴ represents a hydrogen atom, a linear, branched or cyclicalkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20carbon atoms, an aralkyl group having 7 to 20 carbon atoms, ahydroxyalkyl group having 2 to 20 carbon atoms, an alkoxyalkyl grouphaving 2 to 20 carbon atoms, an acyloxyalkyl group having 2 to 20 carbonatoms, an alkylthioalkyl group having 2 to 20 carbon atoms, or a halogenatom; R¹⁵ represents a single bond, a linear, branched or cyclicalkylene group having 1 to 20 carbon atoms, or an arylene group having 6to 20 carbon atoms; R¹⁶ represents a linear or branched alkylene grouphaving 2 to 20 carbon atoms which may be substituted, and the alkylenegroup may contain one or a plural number of a carbonyl group(s), anether group(s), an ester group(s) and a sulfide bond(s) betweencarbon-carbon bond of the alkylene group; and R¹⁷ represents a linear,branched or cyclic alkylene group having 1 to 20 carbon atoms, or anarylene group having 6 to 20 carbon atoms.
 15. The chemically amplifiednegative resist composition according to claim 3, wherein thecomposition further contains one or more basic compounds represented bythe following general formulae (7) to (9),

wherein each R¹² and R¹³ represent a linear, branched or cyclic alkylgroup having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbonatoms, an aralkyl group having 7 to 20 carbon atoms, a hydroxyalkylgroup having 2 to 20 carbon atoms, an alkoxyalkyl group having 2 to 20carbon atoms, an acyloxyalkyl group having 2 to 20 carbon atoms, or analkylthioalkyl group having 2 to 20 carbon atoms, or R¹² and R¹³ may bebonded to form a cyclic structure with the nitrogen atom to which theyare bonded; R¹⁴ represents a hydrogen atom, a linear, branched or cyclicalkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20carbon atoms, an aralkyl group having 7 to 20 carbon atoms, ahydroxyalkyl group having 2 to 20 carbon atoms, an alkoxyalkyl grouphaving 2 to 20 carbon atoms, an acyloxyalkyl group having 2 to 20 carbonatoms, an alkylthioalkyl group having 2 to 20 carbon atoms, or a halogenatom; R¹⁵ represents a single bond, a linear, branched or cyclicalkylene group having 1 to 20 carbon atoms, or an arylene group having 6to 20 carbon atoms; R¹⁶ represents a linear or branched alkylene grouphaving 2 to 20 carbon atoms which may be substituted, and the alkylenegroup may contain one or a plural number of a carbonyl group(s), anether group(s), an ester group(s) and a sulfide bond(s) betweencarbon-carbon bond of the alkylene group; and R¹⁷ represents a linear,branched or cyclic alkylene group having 1 to 20 carbon atoms, or anarylene group having 6 to 20 carbon atoms.
 16. The chemically amplifiednegative resist composition according to claim 4, wherein thecomposition further contains one or more basic compounds represented bythe following general formulae (7) to (9),

wherein each R¹² and R¹³ represent a linear, branched or cyclic alkylgroup having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbonatoms, an aralkyl group having 7 to 20 carbon atoms, a hydroxyalkylgroup having 2 to 20 carbon atoms, an alkoxyalkyl group having 2 to 20carbon atoms, an acyloxyalkyl group having 2 to 20 carbon atoms, or analkylthioalkyl group having 2 to 20 carbon atoms, or R¹² and R¹³ may bebonded to form a cyclic structure with the nitrogen atom to which theyare bonded; R¹⁴ represents a hydrogen atom, a linear, branched or cyclicalkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20carbon atoms, an aralkyl group having 7 to 20 carbon atoms, ahydroxyalkyl group having 2 to 20 carbon atoms, an alkoxyalkyl grouphaving 2 to 20 carbon atoms, an acyloxyalkyl group having 2 to 20 carbonatoms, an alkylthioalkyl group having 2 to 20 carbon atoms, or a halogenatom; R¹⁵ represents a single bond, a linear, branched or cyclicalkylene group having 1 to 20 carbon atoms, or an arylene group having 6to 20 carbon atoms; R¹⁶ represents a linear or branched alkylene grouphaving 2 to 20 carbon atoms which may be substituted, and the alkylenegroup may contain one or a plural number of a carbonyl group(s), anether group(s), an ester group(s) and a sulfide bond(s) betweencarbon-carbon bond of the alkylene group; and R¹⁷ represents a linear,branched or cyclic alkylene group having 1 to 20 carbon atoms, or anarylene group having 6 to 20 carbon atoms.
 17. A patterning processwhich comprises the steps of forming a resist film on a workpiece usingthe chemically amplified negative resist composition according to claim1, irradiating a high energy beam to the resist film, and developing theresist film after irradiation using an alkaline developer to obtain aresist pattern.
 18. The patterning process according to claim 17,wherein EUV or an electron beam is used as the high energy beam.
 19. Thepatterning process according to claim 17, wherein a substrate having alayer containing chromium at an outermost layer thereof is used as theworkpiece.
 20. The patterning process according to claim 17, wherein aphotomask blank is used as the workpiece.